In this post and several others to follow, I'm taking a look at what we actually, really know about the relationship, or association or whatever we want to call it, between Edward II's queen Isabella of France and Roger Mortimer, lord of Wigmore and later the first earl of March. I'm focusing on the primary source, contemporary or near-contemporary, evidence for what went on between them, and this is the first part of maybe three or four posts on the subject, and deals with events of 1325/26. In future posts, I'll look at chronicle evidence for their relationship, examine if anything might have happened between the two before c. late 1325, look at events of 1327 to 1330, and anything else that occurs to me as I go on. Strap yourselves in; it's going to be a long ride.
The first real indication of a major crisis in the king and queen of England's marriage is Isabella's famous 'there are three people in my marriage' speech, made at her brother Charles IV's court in Paris in response to Edward II's order to her and their son Edward of Windsor to come back to England. The speech is recorded only in the Vita Edwardi Secundi, which does not give the date, though it would appear to have been made sometime between about mid-October and early November 1325. Isabella said:
"I feel that marriage is a union of a man and a woman, holding fast to the practice of a life together, and that someone has come between my husband and myself and is trying to break this bond; I declare that I will not return until this intruder is removed, but, discarding my marriage garment, shall put on the robes of widowhood and mourning until I am avenged of this Pharisee." 
This is an ultimatum to Edward II: another person has come between us, and I feel like a widow and am mourning the end of our marriage. I will not return to you and resume our married life until you send this person away. (Isabella could not even bring herself to utter his name, but the person must be Hugh Despenser the Younger.) However later writers might have interpreted her words, that is what her speech says. It says nothing at all about hating Edward or wanting to bring him down or being in love with Roger Mortimer or even leaving Edward permanently. Whether Isabella really believed that her husband would send Hugh away and she could go back to him, there's no way of knowing without mental telepathy or holding a seance, but that is what she said. It's possible that she used Despenser's intrusion into her marriage as an excuse to rebel against Edward. It's also possible that she genuinely wanted to go back to her husband and to resume their marriage, hoped to return to the pre-1322 era before Hugh Despenser came between herself and her husband in both the private and public arenas, and truly believed that Edward would send Hugh away as she wished. Edward had, after all, grown tired of his previous male 'favourites' Roger Damory and Hugh Audley in c. 1318/19, and although he had grieved for Piers Gaveston for a long time, he had come to terms with it and he and Isabella managed to build a successful and seemingly happy partnership. Perhaps she intended to shock Edward into action, and assumed that if it came down to it and she forced him to make a decision, he would choose her and their son over Hugh Despenser, and would eventually get over the loss of Hugh as he had got over the loss of Gaveston, Damory and Audley. But he didn't choose Isabella; Edward demonstrated over the next few months that keeping Hugh close to him, and defending him against any and all accusations, was his number one priority.
Had Isabella known, or guessed, beforehand that Edward would refuse, and hoped that he would because she didn't want to return to him, as a few later writers have claimed? We don't know. We simply don't. It wasn't only herself she was asking Edward to choose over Hugh; she had their elder son, Edward of Windsor, with her in France. I find it hard to imagine that Isabella thought Edward would prefer it if his son and heir remained in a hostile country rather than give up Despenser, or that she thought he would reject his own son, even if he rejected her. Lisa Benz St John has speculated that as Edward II sent Isabella to France in March 1325 to negotiate a peace settlement on his behalf, the queen might have believed that Edward still relied on her and needed her, despite Hugh Despenser's prominent presence in his life. Benz St John further suggests that Hugh persuading Edward II not to travel to France in September 1325 (see my post) to pay homage to Charles IV for his French lands "must have been the ultimate sign to Isabella that Despenser had supplanted her in a way that Gaveston never had."  Indeed, the fact that Hugh Despenser the Younger now had so much power that he could persuade the king of England not to meet the king of France might well have shocked Isabella profoundly, however much she had grown used to Hugh's political dominance over the previous few years. Although the royal marriage had certainly been going wrong for a good while, and Edward had even confiscated Isabella's lands in September 1324 when he was at war with her brother as though his own wife and queen was an enemy alien, perhaps Edward's failure to travel to France at Hugh's instigation was the final straw which forced Isabella into offering her husband an ultimatum. It may be that even in 1325 Isabella hadn't yet truly grasped just how strong Hugh Despenser's hold over Edward was, until he did Hugh's bidding and agreed not to travel to France. This makes more sense to me than some notion that Isabella was inventing her loathing of Despenser and her distress at the state of her marriage because she and Roger Mortimer were having hawt sex in Paris and she needed an excuse not to go back to Edward. Isabella of France was highly intelligent, competent and a canny politician, not to mention the crowned and anointed queen of England, not some teenager making up a story to her parents because she wanted to sneak out with her boyfriend.
Edward II responded to the queen's declaration during a parliament held in Westminster and London between 18 November and 5 December 1325. No official record of this parliament exists, and again, we have to rely on the Vita Edwardi Secundi. It says that Edward defended Hugh Despenser and claimed that Hugh had never done anything bad to Isabella, and that the queen had once seemed to get on well with Hugh but that now, "someone has changed her attitude". The identity of this person(s?) wasn't specified, and it may be that Edward neither knew nor cared but just thought that 'someone' must have manipulated Isabella. During this parliament, the king ordered all the English bishops to send the queen a letter, which the Vita cites, though the letter itself no longer exists. (The text of the Vita ends abruptly soon after this, perhaps because the author was dead or incapacitated.) The bishops' letter stated, in part, "But as for what you [Isabella] have written, that what your brother the king of France and your other friends of that country intend to do on your behalf, will turn out not to the prejudice of the lord king [Edward II] or anyone else, but to the destruction of Hugh alone...". 
Here we see that Queen Isabella, in a letter which also no longer exists, had stated that she wished the 'destruction' of Hugh Despenser the Younger, and that her brother Charles IV and other French people would help her achieve it. Isabella, still in Paris, wrote (or rather, dictated) a letter to Walter Reynolds, archbishop of Canterbury, on 5 February 1326, in response to the letter recently sent to her by the English bishops. She referred to Edward II as "our very dear and very sweet lord and friend", which is highly unconventional and speaks to Isabella's feelings for her husband (conventional would simply have been "our very dear lord", and in a letter to Edward of March 1325 she repeatedly addressed him as "our very sweet heart"). Isabella called Hugh Despenser the Younger nostre mauvoillant, literally "our evil-wisher" though it can also mean devil, and told Reynolds that the only reason for her failure to return to Edward was that she lived in mortal terror of Hugh. Although she wished nothing more than to be in her husband's company and 'to live and die there', she dared not because Hugh, who was in charge of the king and the whole realm, might hurt and even kill her. She admitted that she had faked friendship towards Hugh before she left England to protect herself, and ended the letter by saying that she was so distressed about the whole situation that she could write no more of it. 
Again, however modern writers might interpret her words, or state that the queen was using her fear of Hugh as a plausible excuse to avoid going back to her husband because she was involved in a passionate relationship with Roger Mortimer, this is what she actually said. Much of the modern interpretation of Isabella's speech of c. October 1325 and her letter of February 1326 involves claiming that she didn't really mean what she said, and claiming that she was only pretending to hate and fear Hugh but actually hated her husband, and didn't want to resume her marriage because she'd fallen in love or lust with Roger. I don't know though. Maybe she did mean what she said? Isn't that at least possible? Hugh Despenser the Younger, who threatened to have barons hanged if they didn't give him the lands he wanted and who imprisoned his own loyal supporters and said he would hurt them if they didn't follow his instructions to the last dot on the i, was a pretty darn scary person, after all. He wasn't Piers Gaveston, who irritated a lot of people but who was, basically, harmless. He wasn't Roger Damory, whose relationship with Edward II bothered Isabella so little that she gave him a lot of expensive gifts, or Hugh Audley, whose relationship with Edward II bothered Isabella so little that Audley was one of her closest allies and high in her favour in 1326/27, after the invasion. None of those men threatened Isabella's relationship with Edward or her position as queen. Hugh Despenser the Younger, on the other hand, was ruthless, calculating, manipulative and frightening beyond the telling of it, and to me, it's entirely possible that Isabella had come to believe both that he might harm her, and that Edward was so much in thrall to Hugh that she couldn't rely on her husband to protect her. I see no reason to think that her fear of him was fake.
Below, Isabella calls Edward II nostre treschier e tresdouche seignur e amy, "our very dear and very sweet lord and friend", and Hugh Despenser the Younger nostre mauvoillant.
The first real evidence for Isabella's association with Roger Mortimer and others comes from a proclamation Edward II ordered all the sheriffs of England to make on 8 February 1326; whether coincidentally or not, this was just three days after Isabella wrote her letter to the archbishop. He stated "...the queen is adopting the counsel of the Mortimer, the king's notorious enemy and rebel, and of other rebels, and that she is making alliances with the men of those parts and other strangers...to come in force with the king's son against England, to aggrieve and destroy the king's men and his people. In case the queen and Edward [of Windsor, their son] come in the ships sent for them by the king with their household only in good manner, according to the king's will and commandment, the sheriff is ordered to receive them honourably and courteously." 
Notice here that there's no suggestion of any intimacy; Edward is referring to Isabella making an alliance with Roger Mortimer and other English exiles, i.e. the other noblemen and knights who had fled from England in and after 1322 following the failure of the Contrariant rebellion (see also below). It's telling that in a biography of Isabella published a few years ago, which is keen to push the idea that by now Isabella was madly in love with Roger Mortimer and repulsed by her husband, the words "and of other rebels" are omitted from this quotation from the Close Rolls, as though Edward was talking about Roger alone. Needless to say, the book also fails to mention that Isabella called her husband "our very dear and very sweet lord and friend", and says that Isabella was lying to her husband in her speech and her letter as though this is a certain fact established by asking her in person.
In this proclamation, Edward says that his queen intends to "destroy the king's men". Almost certainly this is a reference to Isabella's threat some months earlier to destroy Hugh Despenser the Younger. In this context, it's worth noting that sometime not long after 8 November 1325, Edward II came to believe that Hugh had been murdered in Wales, and hastily sent three men there to ascertain what had happened. They returned on 20 November with the news that Hugh was alive and well.  It seems that Edward, and others, thought that his wife had followed through on her threat to destroy Hugh; it was Edward's chamber valet Jack Pyk who told the king that Hugh had been killed (Jak Pyk counta au Roi q’ le dit mons’ Hugh fust tue), presumably repeating a rumour he had heard.
Roger Mortimer wasn't the only enemy of Edward II at large on the Continent - Sir John Maltravers, Sir William Trussell and Sir Thomas Roscelyn were some of the others - but, until Edward II's half-brother the earl of Kent joined them sometime in 1326, he was the highest-ranking of them. Roger was assumed in England, surely with good reason, to be the leader of the band of exiles, and the correspondence of Edward II himself, Hugh Despenser the Younger and other allies of the king almost always referred to the men as "Mortimer and the others" between 1323 and 1326 (Edward and several others often just called Roger "the Mortimer", as above, though interestingly, Hugh Despenser the Younger gave him his full name and title, "Sir Roger Mortimer").
The (blurred!) pic below is part of a letter from Hugh the Younger in Octobr 1324, where he talks of "Sir Roger Mortimer and the other exiles" (sire Rogier de Mortymer e les autres bannis).
Another blurred pic - my camera is really having a bad day - of a letter sent to Edward II by his envoys in France in late 1323, talking of "Roger Mortimer and other enemies of our lord the king" (Rogier le Mortimer et autres les enemys nostre seignur le roi).
In Edward's proclamation of 8 February, Roger is the only 'rebel' named because it's following the pattern of just about every other reference to the Englishmen on the Continent between 1323 and 1326, and note that Edward says Isabella is adopting the counsel of "the other rebels" too. Roger is not being singled out here, and Edward is not stating that Isabella is being intimate with him, he's shocked that his own wife has now allied herself with men he deems his deadly enemies and is taking advice from them, and he realises that she and they are serious about bringing down Hugh Despenser. Roger Mortimer and the other English exiles loathed Hugh and wanted him dead as much as Isabella did. While he was alive, they would forever be exiles, separated from their families, lands, income, homeland, and influence. Edward II's proclamation makes clear that by 8 February 1326, he had not heard that the queen's relationship with Roger, or indeed with Maltravers, Trussell and the others, was anything untoward. You'd think that if Isabella's affair with Roger had begun the previous autumn, as some writers believe, Edward II would have heard about it three or four months later.
The part "she keeps his company within and without house" has often been interpreted as Edward II telling his son that Isabella was committing adultery with Roger Mortimer. In the original French, Edward wrote lui se acompaigne en houstel e de hors, often assumed to be a euphemistic way of saying that Isabella had taken Roger as her lover. Maybe it was. Maybe it wasn't. De hors meant 'outside' or 'outside the royal court' more specifically, or 'in public'; houstel meant a house or household, including the royal household; and se acompaigner could mean 'band together' in the sense of taking an ally as well as 'keep someone's company'. Edward also wrote en sa compaigne lui retient de son conseil. En sa compaignie literally means 'in her/his company', but compaignie also means affinity or staff, and Edward II's accounts often use en sa compaignie to refer to his servants when they were being paid their wages every couple of weeks: they had spent the last fourteen days en sa compaignie, i.e. 'with him' or 'working for him'. De son conseil means 'of her council', i.e. the group of Isabella's advisers, and retient means 'retains' in the sense of retaining or engaging a person in your service. So sure, the letter might indeed be Edward II implicitly telling his son that Isabella had taken Roger Mortimer as her lover and was with him 'inside'. It might simply be the king expressing his astonishment and fury that his wife had taken on a man he deemed a traitor and his mortal enemy as her adviser and as a member of her retinue, and furthermore, permitted him to act as their son's counsellor. It might mean that Isabella was not only taking Roger's advice within her own court, but had made her retention of him as a member of her council and as her chief ally against the loathed Hugh Despenser publicly known in Paris.
Many of the English servants Isabella had with her in France, whom she was unable to pay because Edward cut off her funding in mid-November 1325, made their way back to England, where Edward II greeted them with gifts of cash and re-assigned them to positions in his own household. The earliest example of this I can find is one of the queen's cooks, John de la Marche, who returned to England on 30 November 1325 (Isabella's other cook was Will Balsham, who also went back to England sometime in late 1325 or in 1326 and became one of Edward's cooks). Thomas Gurton, one of Isabella's chamber valets, John Dene, usher of her chamber, and Henry Pletour, who looked after her horses, were back in England by 3 December, and on 9 December Robert Sendal, marshal of the queen's hall, returned too. Brother Roger Querndon, confessor of Edward and Isabella's teenage son Edward of Windsor, was back in England by 12 January 1326, Isabella's squire Nicholas de la Despense was back by 20 January, and in late 1325 and early 1326 other servants of the queen also made their way home. The latest reference I can find is to a returned servant is Thomas Martel, one of Isabella's huntsmen, re-assigned as one of the valets of Edward II's household on or before 12 April 1326.  There were, therefore, numerous people who had worked for Isabella in France and then went to work for Edward II, who would have been able to tell the king (or someone in his retinue) if they had seen anything amiss in the queen's association with Roger Mortimer and the other English exiles. Apparently, by 8 February 1326 no-one had, and the claim by one author that Edward paid the men generous sums of money because they brought him news of his wife's affair with Mortimer is unsupported. These men hadn't been paid for weeks; there's no reason to invent some hidden scandalous reason for Edward giving them money and jobs. The way Jack Pyk, chamber valet, told the king in November 1325 that he had heard Hugh Despenser had been killed in Wales shows how Edward's servants were able to share bad news with him, even bad news that affected him personally.
Edward II sent a letter to his and Isabella's thirteen-year-old son Edward of Windsor on 18 March 1326, addressing him affectionately as Beaufuitz or 'fair son'.  By now, the king had given up writing to his queen and did not, as far as the extant record shows, contact Isabella again directly after 1 December 1325. His utter fury with Isabella is apparent in the way he referred to her throughout 1326 abruptly as "our wife", rather than as "Lady Isabella, queen of England, our dearest wife" as he had done before. The king devoted part of this letter to defending Hugh Despenser, and said, in the translation that appears in the Close Rolls, that Isabella "draws to her and retains in her company of her council the Mortimer, the king's traitor and mortal enemy, attainted and adjudged in full parliament, and keeps his company within and without house...[and] she has delivered you [Edward of Windsor] to the company of our said enemy, and makes him your councillor".
Edward II sent another letter to his son on 19 June 1326, in which, although he still called his son Beaufitz, he warned him of the dire consequences of disobeying his lord and father ("you will feel it all the days of your life", vous le sentirez a touz les jours de vostre vie).  Edward had by now heard that his wife and son had been accompanied by Roger Mortimer during the recent coronation of Charles IV's third wife Jeanne of Evreux: "you notoriously kept company with and adhered, and your mother also, to the Mortimer, our traitor and mortal enemy, in the company of your mother, and elsewhere". Evidently Edward of Windsor had sent at least one letter to his father, which does not survive, in which he protested that Mortimer was not an adherent of himself or his mother. As Roger had, however, during the coronation, publicly carried vostre suyte, "your suit of clothes", the teenage boy's father knew he was being untruthful. So this is evidence that by May/June 1326, Isabella was willing to appear in public with Roger Mortimer, and also that Roger had taken on an official role with her son as well and was spending time with him, on some occasions without his mother there. I suppose this is the kind of evidence that, if you want it to be, proves that Isabella was flaunting her affair with Roger in front of her family and French courtiers. If you don't, it's simply the queen and her son spending time during a public ceremony with an English baron who's an adviser to them both, who shares their dismay at Hugh Despenser's dominance of their husband/father, and who, like them, is desperate to see him gone.
One of the charges that was presented at Roger Mortimer's trial in November 1330, but must be referring to 1326 or 1327, states:
"Item, the said Roger falsely and maliciously initiated discord between the father of our lord the king and the queen his consort, and he caused her to believe that if she came to him he would have killed her with a knife or murdered her in another manner. Because of which, for that reason, and by his other subtle scheming, he caused the said queen not to come to her said lord." 
The bit about the knife says, in the original French, si ele feust venue a lui q'il la eust tuez d'un cotel ou en autre manere murdre. In both the original and in translation, the meaning of the 'he' or il who would stab Isabella if she went back to her husband is unclear; does it mean Roger Mortimer, or Edward II? In my view, it's more likely to be a reference to Edward; in 1326/27, some people, especially churchmen, grew uneasy at Isabella's failure to return to and live with her husband (before and after his deposition). Her ally Adam Orleton, bishop of Hereford, came up with the idea that the queen would be in danger of violence from Edward if she returned to him, as a plausible reason for her living apart from him. Supposedly Orleton claimed in a sermon that Edward carried a knife in his hose to kill his wife, and said that if he had no other weapon he would "crush her with his teeth". 
Even if it does mean Roger, there are other reasons besides sexual jealousy why he might have reacted with murderous fury if Isabella decided to go back to her husband sometime in 1326 before they'd gathered forces and ships to launch their invasion. Roger had been on the run since his escape from the Tower in August 1323, and without Isabella and her control of her adolescent son, he and the other English exiles would have no chance of bringing down Hugh Despenser (and ultimately Edward II as well, if that was their plan). They'd remain exiles on the Continent who could never go home or see their families. Hugh Despenser the Younger heard as early as October 1324 that the English exiles intended to land with their forces in Norfolk or Suffolk, as indeed they did, just under two years later (Hugh had a spy in the exiles' company who sent him information about them). He knew they were talking to the count of Hainault and asking him to help them.  But before Isabella joined them, they didn't invade England, because how would they pay for soldiers and ships without the marriage of the future king of England to sell to the count of Hainault, and why would he help them unless he got something pretty massive from them in return? A previous attempt to send assassins after Hugh and his father had also failed.  It's hardly a wonder if Roger raged at the prospect of Isabella and her son going back to England and taking no further part in the rebellion.
This post is going to peter out lamely now as I've run out of energy to research or write any more, haha. But there's absolutely tons more to come soon!
1) Vita Edwardi Secundi, ed. Wendy Childs, p. 243.
2) Lisa Benz St John, 'In the Best Interest of the Queen: Isabella of France, Edward II, and the Image of a Functional Relationship', Fourteenth Century England VIII, ed. J.S. Hamilton (2014), pp. 37-40.
3) Vita, ed. Childs, pp. 245-7.
4) Historiae Anglicanae Scriptores Decem, ed. Roger Twysden (1652), column 2767-8.
5) Calendar of Close Rolls 1323-27, p. 543.
6) Society of Antiquaries of London, Manuscript 122, pp. 34, 37-8.
7) SAL MS 122, pp. 40-42, 46, 49, 59.
8) CCR 1323-27, p. 578; Foedera 1307-27, p. 623.
9) CCR 1323-27, pp. 576-7; Foedera 1307-27, pp. 630-31.
10) The Parliament Rolls of Medieval England, ed. Chris Given-Wilson et al, November 1330 parliament.
11) Roy Martin Haines, 'The Stamford Council of April 1327', English Historical Review, 122 (2007), pp. 142-4; PROME, January 1327 parliament.
12) Pierre Chaplais, ed., The War of Saint-Sardos (1323-1325): Gascon Correspondence and Diplomatic Documents, p. 72.
13) Calendar of Patent Rolls 1321-24, p. 349.