A post on Edward II's eldest nephew Gilbert de Clare, earl of Gloucester and Hertford.
Gilbert was born on or about 10 May 1291 at Winchcombe in Gloucestershire, eldest child of Gilbert 'the Red' de Clare, who was forty-seven going on forty-eight, and Joan of Acre, who was nineteen and the second surviving daughter of Edward I. The couple had married a little over a year earlier. Gilbert was christened by Robert Burnell, bishop of Bath and Wells and chancellor of England, and Edward I gave the whopping sum of £100 to the messenger who brought him news of the birth (by way of comparison, he gave the messenger who brought him news of the birth of Gilbert's half-sister Mary de Monthermer five marks, or three and a third pounds).
Gilbert was the eldest grandchild of Edward I, who was fifty-one in early May 1291. His grandmother Eleanor of Castile had died on 28 November 1290 the previous year, so didn't live long enough to see her grandson - though she may have known that Joan was pregnant. He had two much older half-sisters from his father's first marriage, Isabel and Joan, born 1262 and c. 1264, three full sisters Eleanor, Margaret and Elizabeth, and four half-siblings from his mother's second marriage. His father died when Gilbert was four, in December 1295.
Gilbert is often said to have been a member of his uncle Edward II's household before he became king. This is incorrect: the Gilbert de Clare who lived in Edward's household was Gilbert's first cousin of the same name, the eldest son of Gilbert the Red's brother Thomas de Clare (died 1287).  This Gilbert was lord of Thomond, born in 1281 and died in 1307. Probably in 1306, he married Hugh Despenser the Elder's daughter Isabel, in a joint de Clare-Despenser alliance; Eleanor de Clare, eldest daughter of Gilbert the Red and Joan of Acre, married Hugh Despenser the Younger in May 1306. Joan of Acre had been granted the marriage of Gilbert de Clare, lord of Thomond, in July 1294.  Gilbert (the one this post is about, not his cousin of Thomond; why were they so unimaginative with names?) was seven years younger than Edward II, not much of an age gap between uncle and nephew, but too big for him to have been much of a companion to Edward in adolescence and early adulthood.
In fact, Gilbert, from the age of ten, grew up in the household of his step-grandmother Queen Marguerite, who was only about ten or twelve years his senior: on 27 September 1301, his grandfather Edward I issued a "mandate to Joan, countess of Gloucester and Hertford, the king's daughter, to deliver to Margaret, queen consort, on her demand Gilbert, son and heir of Gilbert de Clare, sometime earl of Gloucester and Hertford, tenant in chief, and of the said Joan, as it is the king's will that he shall stay in the queen consort's custody until further order."  Although some writers have chosen to see this order as Edward I's punishing Joan for marrying Ralph de Monthermer without his permission, or proof that Joan was an unfit mother, it was of course an entirely normal thing to do.
Joan of Acre died on 23 April 1307, shortly before Gilbert's sixteenth birthday. Two and a half months later, his grandfather Edward I died, and his twenty-three-year-old uncle acceded as Edward II. On 18 August, Edward II granted Gilbert "all lands of his inheritance in Wales, which by reason of his minority are in the king's hands, together with all the appurtenances of that inheritance in England, Ireland and Wales, subject to a yearly payment to the Exchequer of 1000 marks for the lands in Wales," and on 26 November, permitted Gilbert "to hold all his father's lands, which are in the king's hands by reason of his minority, the king, out of his affection for him, having restored them to him in order that he may receive knighthood and serve the king."  This was five years before Gilbert could normally have expected to inherit; he would have come of age on 10 May 1312. Presumably Edward knighted Gilbert soon afterwards.
Edward's motives for granting Gilbert his inheritance so early are uncertain - desire for an ally, affection for his nephew, a sop so that Gilbert would accept his sister Margaret's marrriage to Piers Gaveston - but of course Gilbert-the-wealthy-earl was far more politically useful to Edward than Gilbert-the-underage-ward. At the age of sixteen, Gilbert now had an annual income of £6000, and was the richest man in the country after his uncle the king and his cousin the earl of Lancaster. On 12 March 1308, Edward also granted Gilbert the right "to marry whomsoever he will," and he chose Matilda (or Maud), one of the daughters of Richard de Burgh, earl of Ulster. They married at Waltham Abbey on 30 September 1308, in Edward II's presence. Gilbert was seventeen.  Many of the magnates had planned to hold a Round Table jousting tournament at the wedding, "but some of them were afraid of being beset, and dreaded treachery, so that the plans came to nought." 
The behaviour of Edward II and Piers Gaveston in 1308 put Gilbert in a rather awkward position, as he was Edward's nephew and Piers' brother-in-law. His actions are rather obscure, but he seems not to have actively supported the pair, nor to have actively opposed them. After Piers' exile in June 1308, however, Gilbert soon came back to his uncle's side, and witnessed Piers' restoration to the earldom of Cornwall on 5 August 1309.  A few weeks later, Edward issued a "notification that the hospitality shown, at the king's request, by the archbishop of York, at his dwelling house at Thorpe near York, to Gilbert de Clare, earl of Gloucester and Hertford, is not to be a precedent for imposing a like charge upon him and the church of St. Peter, York, on any future occasion." 
After his return from exile, Piers Gaveston is said to have nicknamed Gilbert filz a puteyne, 'whoreson', supposedly a malicious reference to his mother Joan of Acre’s secret marriage to the squire Ralph de Monthermer in 1297. However, it’s possible that this referred to Ralph himself, Edward II’s brother-in-law, as he was apparently illegitimate. It seems unlikely that Piers would insult Edward II’s sister in such a public fashion. Also, Gilbert seems to have been on perfectly amicable terms with his brother-in-law in 1309 and 1310, which surely argues against the notion that Piers had called Gilbert's mother a whore. Still, Gilbert's support of his uncle and brother-in-law wavered on occasion: he refused to attend the parliament Edward summoned to York in October 1309 and again in February 1310, though he did attend the Westminster parliament in March 1310. He was one of the four earls, the others being Lincoln, Richmond and Surrey, whom Edward appointed to ensure that no-one came to parliament armed, with power "to settle all quarrels and punish offenders."  In fact, the earls of Pembroke, Arundel, Lancaster, Warwick and Hereford did come armed.
It was at the Westminster parliament that Edward was forced to consent to the formation of the Lords Ordainer, who appointed themselves to "ordain and establish the state of our household and our realm, according to right and reason…for the good of ourselves and of our realm."  Gilbert was elected as one of the Ordainers; of the eleven earls, only three were not: Cornwall (Piers Gaveston), Oxford (the totally insignificant Robert de Vere, who played no role in Edward II's reign) and Edward's nephew-in-law Surrey, John de Warenne.
Despite his role as an Ordainer, however, Gilbert chose to accompany his uncle on his what-not-at-all-surprisingly-turned-out-to-be-unsuccessful-and-pointless year-long Scottish campaign that autumn, with only two other earls - Cornwall and Surrey - and they set off for the north in August 1310. Gilbert spent the next few months at Norham Castle, presumably accompanied by his wife Matilda - Queen Isabella and the countesses of Cornwall and Surrey were certainly in the north with their husbands. Although nothing is known about Gilbert and Matilda's relationship, they are thought to have had a son named John born in April 1312, who presumably died soon afterwards as Gilbert was childless at the time of his death in 1314. [Can't remember the source for John, I'm afraid, and I'm too lazy to go and look.]
In early February 1311, the earl of Lincoln, whom Edward had left as regent of England in his absence, died in his late fifties. On 4 March, Edward appointed Gilbert as keeper of the realm instead, a great responsibility for the young man, not yet twenty.  Gilbert returned south to take up his duties and to help the Ordainers with their reforms of Edward's household. Unfortunately, Gilbert became embroiled in a feud with his cantankerous cousin the earl of Lancaster; relations between the two men were so bad that an anonymous letter-writer said that he feared a riot when the two men arrived in London. 
Parliament opened at Westminster in August 1311, and Gilbert was one of the Ordainers who tried to persuade Edward to send Piers into exile again. After they finally got him to agree - it took nearly two months - Edward ordered letters testifying to Piers' good character and loyalty to be written, and at his uncle's request, Gilbert added his seal. He then changed his mind and tore it off, "excusing himself on the grounds of his minority." 
Piers Gaveston returned to England yet again in early 1312. Gilbert met the other Ordainers at St Pauls early that February, and five of them bound themselves by oath to capture Piers. Gilbert was not one of them, but did promise to ratify whatever the others did.  After the earl of Warwick captured Piers in June 1312, the earl of Pembroke begged Gilbert to help him rescue the Gascon. Gilbert evidently was by then sick of his brother-in-law and refused to help, telling Pembroke that Warwick had acted with his aid and counsel. Pembroke had pledged all his lands to ensure Piers' safety, and Gilbert added "It only remains to advise you to learn another time to negotiate more cautiously."  The reaction of the fortyish Pembroke to this condescending pronouncement by a twenty-one-year-old is sadly not recorded. After Piers' death, however, Gilbert worked tirelessly to reconcile Edward and the earls of Lancaster, Warwick and Hereford.
The next important event in Gilbert's life was in May 1313, when Edward II once more left his nephew as keeper of the realm when he travelled to France with Isabella (it was during this trip that Edward watched 54 naked dancers). And thirteen months later, Gilbert was one of only three English earls, the others being Hereford and Pembroke, who fought for Edward II at Bannockburn. The first day of the battle, Saturday 23 June, saw a series of skirmishes which went the way of the Scots. Gilbert, rather humiliatingly, was unhorsed. He and his uncle by marriage the earl of Hereford had a row about who should lead the vanguard of the English army, Gilbert being constable of the army, Hereford being constable of England.
That night, Gilbert tentatively suggested to Edward that they should take a day's rest and allow the army to recuperate, not least because the following day was not only a Sunday but a holy day, the feast of the Nativity of St John the Baptist. This was a perfectly reasonable suggestion, but Edward, unjustly, accused his nephew of cowardice and deceit. Gilbert's reaction is not recorded, but I can't help seeing him as going purple in the face then dashing outside to kick the nearest object while muttering heartfelt oaths at the supremely annoying uncle who had just maligned him in public.
The following day, Gilbert, desperate both to lead the vanguard and to prove Edward's accusations false, cried out "Today, it will be clear that I am neither a traitor nor a liar" and set off at a gallop towards the Scottish schiltroms, his men following closely behind. In his haste, he made the horrible mistake of forgetting to put on the surcoat which identified him as the earl of Gloucester, came off his horse and "was pierced by many wounds and shamefully killed."  Had the Scots known who he was, they would have taken him alive in order to claim an enormous ransom. Gilbert was then twenty-three.
Robert Bruce treated Gilbert's body with great honour and respect. He personally kept an overnight vigil over the body, and sent it back to England with full military honours, at his own expense. Although the two men had almost certainly never met, they were second cousins - Bruce's paternal grandmother Isabel de Clare was the sister of Gilbert's grandfather Richard de Clare - and married to sisters, Matilda and Elizabeth de Burgh.
Gilbert was buried at Tewkesbury Abbey with his father, grandfather, great-grandfather and other members of the de Clare family, and presumably his remains are still there. Edward II's Wardrobe account for 8 August 1317 says that five shillings and sixpence were given "in oblations distributed at diverse masses celebrated in the presence of our lord the king, in the conventual church of Sheleford for the soul of the Lord Gilbert de Clare, late earl of Gloucester, deceased, whose heart lies there inhumed." . Edward II's itinerary shows that he was indeed at Shelford, just outside Nottingham, on that day, though this is the only reference I know of to Gilbert's separate heart burial.
The death of Gilbert de Clare, earl of Gloucester and Hertford, had a profound effect on Edward II's reign. Not only was the king deprived of his nephew, loyal to him and generally a moderate and calming influence but also respected by the barons as the scion of an ancient noble family and grandson of the old king, but Gilbert's childless death meant that his vast lands and wealth would ultimately pass to the ambitious and unscrupulous men who were his brothers-in-law; precisely what Edward II’s England needed least. There's a great 'what if?' of Edward's reign: what if the earl of Gloucester had remembered to wear his surcoat at Bannockburn?
1) Hilda Johnstone, Edward of Carnarvon 1284-1307 (1946), p. 75.
2) Calendar of Patent Rolls 1292-1301, p. 81.
3) CPR 1292-1301, p. 606.
4) Calendar of Close Rolls 1307-1313, p. 10; CPR 1307-1313, p. 1.
5) CPR 1307-1313, p. 50.
6) Vita Edwardi Secundi, ed. N. Denholm-Young (1957), p. 6.
7) CCR 1307-1313, pp. 225-226.
8) CPR 1307-1313, p. 195.
9) CPR 1307-1313, pp. 206-207; Foedera, p. 103.
10) Foedera, p. 105.
11) CPR 1307-1313, p. 333; Foedera, p. 129.
12) J. R. Maddicott, Thomas of Lancaster 1307-1322: A Study in the Reign of Edward II (1970), p. 115.
13) Vita, pp. 20-21.
14) Vita, pp. 22-23.
15) Vita, p. 26.
16) Vita, pp. 52-53.
17) Thomas Stapleton, ‘A Brief Summary of the Wardrobe Accounts of the tenth, eleventh, and fourteenth years of King Edward the Second’, Archaeologia 26 (1836), p. 341.