William; born 20 Nov 1253; summoned to serve against Welsh 1277, 1282 and 1283, also to an embryonic form of Parliament 1283; married Elizabeth and died by 16 Sep 1295. [Burke's Peerage]
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William de Say IV, probably by 2nd wife (stated without evidence), b. 20 Nov 1253, d. on or bef. 16 Sep 1295; m. Elizabeth, who survived him. [Magna Charta Sureties]
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WILLIAM DE SAY IV, son and heir, was born 20 November 1253. The wardship of his father's lands and heir had been granted by the King to Poncius de Mora, King's merchant, in discharge of the King's debts to him; but by September 1273 William had bought the custody of the lands. On 27 July 1276 he was granted protection, being about to go to Ireland for 3 years. In 1277 he was summoned to be at Worcester on 1 July to serve in person against Llewellin Prince of Wales; John de Say seems to have served in his place. In 1282 and 1283 he was summoned to Worcester to serve against the Welsh. By writ dated 30 September 1283 he was summoned to attend the Parliament at Shrewsbury. In 1287 he was summoned to appear with horses and arms at a military council at Gloucester: in 1294 to attend the King on urgent affairs immediately upon receipt of the writ, dated 8 June. On 14 June 1294 he was ordered to attend the King at Portsmouth on the affairs of Gascony; and on 15 July 1294 he was granted protection as going with Edmund the King's brother to Gascony. He married Elizabeth (b). He died on or before 16 September 1295. [Complete Peerage XI:473-4, (transcribed by Dave Utzinger)]
(b) After his death she was assigned as dower the manors of Cudham (Kent) and Hamsey (Sussex) with an annual payment from the manor of Birling (Kent).