Piers was killed at Blacklow Hill in Warwickshire on Monday 19 June 1312 - see this post, and Anerje's great blog about Piers, for more details. On that day, Edward II was staying 150 miles away at Burstwick-in-Holderness near Hull, with Queen Isabella, who was about four months pregnant with Edward III. Let me emphasise the fact that Isabella was already pregnant when Piers died; too many websites give the impression that Edward only began a proper relationship with his wife after the death of his favourite, as though the killing of Piers Gaveston was a necessary step to ensure the continuation of the royal English line.
Over the next few days, the royal couple travelled via Beverley and Pocklington to York, where they arrived on 24 June. We can probably assume that Edward was concerned about his friend's well-being - the earl of Pembroke had been taking Piers south to attend parliament following his surrender at Scarborough Castle, when he was abducted by the earl of Warwick at Deddington - but it never seemed to occur to him that Piers' life might be in danger from their enemies, and royal business went on much as usual: Edward borrowed forty pounds from the Genoese merchant Antonio di Pessagno to buy pearls for Isabella (yes, that's jewels for Isabella, a payment recorded in plain view on the Close Roll but conveniently ignored by the kind of writers who like to drone on about how Edward ignored and, of course, frequently 'abandoned' his queen), sent his servant John de la Marche to retirement at the priory of Bridlington, and pardoned two men for outlawry. Etc, etc.
It was on 26 June, a week after the event, that Edward learned of Piers' death - or, at least, responded to it. There was a sudden flurry of activity on that day: Edward gave custody of Piers' castles at Wallingford, Knaresborough and Tickhill to three men, one of whom (William de Vallibus) had previously acted as Piers' attorney, and another (Edmund Bacun) who had been granted custody of some of Piers' lands after his third exile in late 1311. In February 1312, the Ordainer William Martin had captured and imprisoned two of Piers' retainers, Bertrand Assailit and Berduk or Bernard de Marsan - the latter presumably a relative of Piers, as Marsan was his mother's name - with 1000 marks Piers had asked them to bring to him from Cornwall. Edward ordered Martin to send this money to the earl of Pembroke, also on 26 June - evidence that he knew Piers was dead, and evidence also that he didn't blame Pembroke, who had sworn to protect Piers, for his friend's death.
Four more things happened on 26 June: Edward wrote to the mayor of London, ordering him "to take the city of London into the king's hands without delay, and to guard it for the king's use," and wrote also to the treasurer and the constable of the Tower of London, ordering them to fortify the castle with men, armour and victuals. Rather mysteriously, the king told the keeper of the manor of Burstwick to deliver from the stud-farm there one bay horse each for his cousin Henry Beaumont, his steward Edmund Mauley, and his squire Oliver de Bordeaux. And he gave custody of the castle of Scarborough, where Piers had been captured a few weeks before, to the excellently-named Tallifer de Tilliolo. (I don't know who Tallifer was, but rest assured I will do my utmost to find out.)
The Vita Edwardi Secundi records Edward's reaction to Piers Gaveston's death as follows:
"By God’s soul, he acted as a fool. If he had taken my advice he would never have fallen into the hands of the earls. This is what I always told him not to do. For I guessed that what has now happened would occur. What was he doing with the earl of Warwick, who was known never to have liked him? I knew for certain that if the earl caught him, Piers would never escape from his hands."
Paul Doherty, in the author's note to his recent novel The Darkening Glass, suggests that Edward's reaction to Piers' death was "strangely muted," and a theme of the novel is that Edward had grown tired of his friend. Well, not really. Edward's words do sound rather odd, but as I've pointed out before, this is probably nothing more than evidence that profound shock, grief and rage do not lend themselves to eloquence. The Vita and several other chronicles, such as Lanercost, Scalacronica and Anonimalle, point out that Edward swore revenge for Piers' death, and if we look at Edward's subsequent actions rather than his speech, we get a far more reliable indicator of his feelings about Piers and his death. As late as June 1326, fourteen years later, Edward was still paying numerous religious houses to pray for Piers' soul, hardly the actions of a man who had tired of him. The king spent large sums of money on taking care of Piers' mortal remains - spending, for example, £144 between 8 July 1312 and 7 July 1313 on wax for candles to burn around Piers' body, eighty pence a day to the Dominicans of Oxford to pray over the body, £300 on cloth of gold to dress Piers for the funeral, and fifteen pounds to two men to watch over the body - for only twenty-eight days in December 1314! These are huge, huge amounts of money - the kind of money you spend on a person you adore, not a person you'd grown tired of or no longer cared about.
Edward left York on 28 June 1312, two days after he heard about or at least responded to Piers' death (I have no idea who told him, by the way; I assume the earl of Pembroke sent a messenger) and headed south to London. He left the pregnant queen behind, presumably to keep her out of the way of any danger, given that there was a strong risk that the country would slide into civil war - though I'm sure proponents of the currently oh-so-trendy Isabella Was A Tragic Neglected Victim Of Her Callous Husband theory can find some way of twisting this into more evidence that he was 'abandoning' her. Apparently, however, Isabella herself didn't think so: she sent a letter to Edward on 29 June, the day after his departure. This cannot have been her reaction to hearing about Piers' death as postulated by various writers, who miss the fact that she was with Edward when he heard about it.
Edward II's extant accounts provide a fascinating insight into his journey from York to London through Lincolnshire. On 30 June, he paid Graciosus the Taborer (drummer) for playing for him at Howden. He stayed at Swineshead Priory on 6 and 7 July, and paid another pound to Janin the Conjuror for his performance in the king's private chamber. (Isn't that a wonderful image - the twenty-eight-year-old king of England watching conjuring tricks in his room at a priory on a summer evening?) On 8 July, Edward had reached Surfleet, and gave three shillings to William the Acrobat and his fellows for "making their vaults" before him.
The king arrived in Westminster on 14 July and stayed there for the rest of the month, and made an impassioned public speech at the house of the Dominicans asking the Londoners to defend the city against Piers Gaveston's killers; evidence that Edward could be eloquent when the mood took him and when he cared deeply about something. For once, London supported him and closed the gates of the city against the earls of Lancaster, Warwick and Hereford, who brought their armies to Hertfordshire. On the other hand, the king summoned the three earls to appear before him at Westminster or London, playing a double game, as he often did; Edward had an aptitude for political intrigue, if little else. Rumours swirled: that Edward intended to seize Lancaster as soon as he entered London; that Lancaster would, with the help of a group of Londoners, capture Edward in the city. The killing of the king's favourite ensured that England teetered on the brink of civil war...