helped De Montfort in his attack on the Bishop of Hereford (Dunst. Ann. 220–2; Rymer, i. 425; Wykes, i. 133), but held aloof from politics for a few months afterwards. He was probably among the many nobles who, according to Rishanger (Camd. Soc. 15), went over to the royal side about October (cf. Wykes, 140). But by the early part of April 1264 he must have been in open rebellion against the king, for he seems to have conducted the massacre of the Jews in Canterbury about the same time that de Montfort was slaughtering those of London (c. 10 April). A little later Henry seized his castle of Kingston on his way to the relief of Rochester, and very shortly after this captured the Countess of Gloucester at Tunbridge Castle. The lady, however, being the king's cousin, was set free (Dunst. Ann. 230; Rishanger, Rolls Series, 22). Gloucester was now recognised as the second leader of the baronial party. The negotiations immediately preceding the battle of Lewes were conducted in his name and that of De Montfort, and both were publicly denounced as traitors on 12 May. Just before the engagement (14 May) Simon knighted Gilbert and his brother Thomas (Ann. Wint. 451). In the actual battle the young earl led the centre of the baronial army (Prothero, 277); and it was to him that the king surrendered his sword when the day was lost, knowing him to be ‘nobiliorem et ceteris potentiorem’ (Wav. Ann. 357).
From this moment the Earls of Leicester and Gloucester were supreme. The mise of Lewes contained a special clause exempting them from any punishment for their conduct (Rishanger, Camd. Soc. 38). By the arrangement of 9 June they were empowered to nominate a council of nine, in concert with the Bishop of Chichester (Rymer, 444). On 20 Nov. Guido, the papal legate, excommunicated Gloucester along with other rebels (ib. 447). Ten days later (30 Nov.) the first mutterings of disagreement between Leicester and Gloucester may have broken out at the Oxford parliament, which was called to discuss the conduct of the royal partisans who had taken refuge in the marches (Oseney Ann. 154). Gilbert was with the king and Simon at Gloucester when the marcher lords were banished to Ireland for a year. Owing to the quarrel of the two earls the lords neglected to obey the order of exile, and by Gilbert's connivance remained in the kingdom (Lib. de Ant. Leg. 70; Wykes, 159). According to Robert of Gloucester (550) it was owing to Earl Gilbert's opposition to Leicester's measures that the great London parliament (14 Jan. 1265) was summoned. The quarrel was already notorious, and Simon openly charged Gloucester with protecting the marchers. According to one chronicler a reconciliation was now effected; but at the best it was only momentary (Ann. Wav. 358; Wykes, 159; Robert of Gloucester, 152). A rumour went abroad that Leicester meditated shutting up Gilbert in prison. The young earl was required to find surety for his future conduct; a tournament that he had made arrangements for holding with young De Montfort at Dunstable was abruptly forbidden (17 Feb.), and Llewellyn was suffered to ravage his Welsh lands (Wykes, 159; Rymer, 450; Wav. Ann. 358). Indignant at such treatment, the earl fled to the marches.
Besides the general complaint that Simon monopolised too much of the government, Gilbert complained that the forfeited lands were not fairly divided, that the king was led about at the beck of the Earl of Leicester, and that the prisoners made by himself and his men had been taken from them. Two charges against the Earl of Leicester are specially noteworthy: first, that the royal castles were kept in Leicester's hands, and garrisoned by French troops; secondly, that the provisions of Oxford were not properly carried out. These complaints reappear frequently in Gilbert's history, and seem in later years to have inspired his whole political conduct (Rishanger, Rolls Series, 32; Trivet, 263; Ann. Wig. 453; Lib. de Ant. Leg. 73).
From a comparison of texts it would seem that Gilbert fled to the marches between 17 Feb. and 24 Feb. (Wav. Ann. 358, with which cf. Rymer, 450); but the feud does not seem to have been recognised till he refused to appear at a tournament to be held at Northampton (13 April or 21 April), immediately after which (25 April) the king, Prince Edward, and Simon started for the marches (Dunstable, 238; Wykes, 161–2; Wav. 361), and entered Gloucester, from which town they held a fifteen days' negotiation with Gilbert, who was then in the Forest of Dean. On 12 May the two earls were nominally once more at peace (Wav. 361–2; cf. Rymer, 455). It was probably between May 12 and 20 that Gilbert attempted to seize the king and Simon on their way to Hereford; but the attempt failed, and there does not appear to have been open warfare till the escape of Prince Edward (26 May). At Ludlow the prince and the young earl met; the former took an oath that, if victorious, he would renew the ‘old good laws,’ and remove the aliens from the royal council and the custody of the royal castles. By 8 June Gilbert and Edward were both proclaimed rebels, and about the same time got possession of Gloucester (Pat. Rolls, 37 a; Wav. 361–2; Lib. de Ant. Leg. 73;
