16812994William de Say's entry in The Complete Peerage
G. H. White, ed., The Complete Peerage of England, Scotland, Ireland, Great Britain, and the United Kingdom Extant, Extinct, or Dormant, 2nd edition, volume XI (1949), pages 470-473.

Page 470:

WILLIAM DE SAY III, s. and h., had sailed with his father to France,(i) and on 26 Aug. 1230 was at Lucon, where the King took his homage for all the lands which his father had held in chief.(j) On 10 Feb. 1232 he was forbidden to go to a tournament at Blyth, because of business to be done in the march of Wales.(k) On 8 Aug. 1233 he was given by the King two bucks in the forest of Essex.(l) On 20 Mar. 1235 he was at Chippenham, where he and Geoffrey de Say, presumably his br., witnessed a charter of Maud de Mandeville, Countess of Hereford and Essex.(m) In 1235 his lands in Kent were taken into the King’s hand because the King had been informed that he had taken part in a tournament at Cambridge; but he proved that at the time he was before the Justices in Eyre in Sussex, and his lands were restored.(n) On 20 Dec. 1235 the Constable of Dover was ordered to permit him to postpone the building of his house in Dover
(i)Patent Rolls, 1225-32, p. 360.
(j)Close Rolls, 1227-31, pp. 431-32; Exc. e Rot. Fin., vol. i, p. 202.
(k)Close Rolls, 1231-34, p. 131.
(l)Idem, p. 244. These gifts with other marks of favour recur frequently throughout his life. Occasionally he was given live bucks and does to place in his park at Sawbridgeworth (Close Rolls, 1234-37, p. 445; 1253-54, p. 168; 1254-56, p. 290 (“ad quendam parcum suum instaurandum”).
(m)Cal. Charter Rolls, vol. i, p. 196.
(n)Close Rolls, 1234-37, p. 212.

Page 471:

Castle until the following Lent.(a) He witnessed the agreement between Henry III and Alexander of Scotland at York in 1237.(b) On 28 May 1238 he was granted protection so long as he should be on pilgrimage beyond seas:(c) and again in 1242 so long as he should be beyond seas with the King.(d) On this expedition he distinguished himself in a skirmish at Saintes on 22 July 1242, capturing the Frenchman John des Barres and 6 knights.(e) He returned to England with Earl Roger Bigod and many others in Oct.(f) On 22 Mar. 1246 he obtained a grant to him and his heirs of free warren in the demesne lands of his manors of Sawbridgeworth and Edmonton.(g) In 1245 he was granted protection so long as he should be in Wales on the King’s service,(h) and the scutage for his fees in Norfolk for the army of Deganwy was paid to him.(i) In May 1246 he was granted a weekly market and a yearly fair at his manor at Linton, and in July a weekly fair at his manor of Bertre.(j) Shortly after Easter 1247, he was party to a fine whereby the manor of Saddlescombe (Sussex) was given to the Knights Templars in exchange for the manor of West Greenwich, which his grandfather Geoffrey had given them.(k) At the same time, he was settling a dispute with William, Earl de Warenne, about the fishery and hunting at Hamsey.(l) On 19 Mar. 1252 he was granted for life the right freely to hunt the wolf, hare, fox, cat, and otter without nets in the river, in all the King’s forests this side Trent, if he take none of the King’s deer.(m) On 6 Aug. 1252 he was sum. to be at Westminster in the quinzaine of St. Michael with horses and arms ready to cross the sea with the King to Gascony.(n) In Dec. 1253 he, with 2 of his knights, was given robes for the coming Christmas festival,(o) and on 20 Dec. he was at Bazas with the King.(p) In 1254, indignant at
(a)Idem, p. 218.
(b)Fœdera, vol. i, p. 234.
(c)Cal. Patent Rolls, 1232-47, p. 222.
(d)Idem, p. 297.
(e)M. Paris, vol. iv, p. 213.
(f)Ann. Mon., vol. i, p. 127.
(g)Cal. Charter Rolls, vol. i, p. 282.
(h)Cal. Patent Rolls, 1232-47, p. 464.
(i)Close Rolls, 1242-47, p. 403.
(j)Cal. Charter Rolls, vol. i, p. 294.
(k)Sussex Rec. Soc., vol. 2 (Suss. Fines), no. 342. The original grant was in 1213-14, and the exchange was first made by William’s father Geoffrey (Dugdale, Mon., vol. vi, p. 840; Suss. Arch. Coll., vol. ix, p. 234).
(l)Sussex Rec. Soc., vol. 2 (Suss. Fines), no. 341.
(m)Cal. Charter Rolls, vol. i, p. 380.
(n)Close Rolls, 1251-53, p. 240; Cal. Patent Rolls, 1247-58, p. 233.
(o)Close Rolls, 1253-54, p. 202; Bémont, Rôles Gascons, vol. i, no. 2889.
(p)Cal. Patent Rolls, 1247-58, p. 259; Bémont, vol. i, no. 2255.

Page 472:

an attack by the Poitevins on Welsh raiders, he with very many others left the army with the King’s leave, and returned to England.(a) In 1260 he was sum. to be in London in 3 weeks after Easter, with the service due to the King,(b) and on 19 May was app. to keep the castle of Rochester.(c) On 11 Aug. he was sum. to join the army of Wales at Shrewsbury with horses and arms and the service due from him, on 17 Feb. 1261 he received orders in connection with his summons to join the King; and on 18 Oct. he was sum. to London with horses and arms.(d) On 17 Oct. 1263 he was ordered to come to the King at Windsor with the horses and arms which he brought to London, to treat of certain matters touching the realm:(e) and in 1264 sum. to be at Oxford in mid-Lent with horses and arms on affairs in Wales.(f) On 9 and again on 11 May 1264 the King sum. him to attend with arms and horses,(g) and he was at the battle of Lewes on 14 May on the King’s side.(h) The Earl of Gloucester seized some of his manors;(i) but the King, on 11 Aug. 1264, directed Gloucester, whose bailiffs had occupied the manors during the recent disturbance, to hand over to Mary, William de Say’s wife, the manors of Birling, Burham, Cudham and Bertre, because she had no means of maintaining herself and her family, and "it was improper and shameful that for lack of sustenance she should be compelled to beg."(j) On 8 Aug. 1265 he was commanded to deliver the County of Kent to Roger de Leyburn.(k) He was certainly completely restored to favour from 1266 onwards, receiving frequent gifts, and obtaining pardons for various offenders.(l) He m.,
(a)M. Paris, vol. v, p. 443.
(b)Close Rolls, 1259-61, p. 158.
(c)Cal. Patent Rolls, 1258-66, p. 71.
(d)Close Rolls, 1259-61, pp. 192, 457, 496, 497.
(e)Cal. Patent Rolls, 1258-66, p. 290.
(f)Close Rolls, 1261-64, p. 378.
(g)Idem, pp. 384, 385; yet on 12 May his tenants in the manors of Birling and Burham were notified that the King had granted the lands to his son, because William was with the King's enemies at the taking of Rochester and siege of the castle (Cal. Patent Rolls, 1258-66, p. 317).
(h)He fled to Tonbridge, where he told the garrison that the Londoners, routed by Prince Edward at the beginning of the battle, would probably seek shelter at Croydon, and, before setting out for Bristol, the garrison fell upon the fugitives and slew many of them in defiance of the royal order to cease hostilities (Knighton, Rolls Ser., vol. i, p. 249).
(i)Cal. Inq. Misc., vol. i, no. 726; cf. nos. 303, 658, 732, 759, 806, 925.
(j)Close Rolls, 1261-64, pp. 354-55.
(k)Cal. Patent Rolls, 1258-66, p. 435.
(l)E.g., Close Rolls, 1264-68, pp. 178, 163, 205, 433; Cal. Patent Rolls, 1266-72, pp. 48, 94, 164, 167, 168. His restoration to favour is mentioned in the passages cited in notes "j" and "k" above.

Page 473:

1stly, Sibyl,(a) and, 2ndly, Mary.(b). He d. before 12 Feb. 1271/2.(c) Mary survived him and m. in or before May 1273. Robert DE UFFORD,(d) Justiciary of Ireland 1276-81, and ancestor of the UFFORD EARLS OF SUFFOLK.
(a)'Will de Sai filius Galfredi de Sai . . . [Noverit unversitas vestra me] pro salute anime mee et uxoris mee Sibille concessisse monachis de Bermundsey ecclesiam de Berlinges quam Walkelinus Maminot predecessor meus et Galfridus de Sai avus meus dederunt et Galfredus de Sai pater meus similiter concessit.' (Thorpe, Reg. Roff., p. 169.) Sibyl was living in Oct. 1250 (Cur. Regis Roll 143, m. 15. d. [See #1449 here.]). According to Edmondson (vol. iv, no. 320) and other 18th cent. pedigree-makers, she was da. of John Marshal of Lenton.
(b)Close Rolls, 1268-72, p. 465; Rot. Hundr., vol. i, p. 236 [You can read an English translation here by searching "Ruxley Hundred."]
(c)Cal. Inq. p.m., vol. i, no. 813; Cal. Patent Rolls, 1266-72, pp. 623, 670.
(d)Cal. Fine Rolls, 1272-1307, p. 5; Rot. Hundr., vol. i, p. 219, p. 236, 529.