134503952William 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 464-465

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SAY(a)

WILLIAM DE SAY I(b) is chiefly known as an associate of Geoffrey de Mandeville, 1st Earl of Essex, in his last revolt, with Hugh Bigod, against Stephen in 1144.(c) In the 2nd charter of the Empress Maud to the Earl, issued between Christmas 1141 and the end of June 1142, William was given a special grant of his father’s lands.(d) According to Henry of Huntingdon, he was killed with the Earl in Aug. 1144 when, after occupying Ramsey Abbey, they were attacking Stephen’s fort at Burwell, Cambs,(e) but there is evidence that William surv. the Earl.(f) He m. Beatrice, divorced wife of Hugh TALEBOT, sister of
(a)So far as is ascertainable, there is only one place in Normandy named Sai: about 2 miles S.E. of Argentan (dep. Orne). There is, however, nothing but the name to connect this family with any place named Sai, except perhaps the statement in Gall. Christ., vol. xi, col. 443, that the Cistercians say that the Abbey of Aunay was founded 15 July 1131 by Jordan “de Saio prope Argentomum” and Lucy his wife. The arms of this family were Quarterly gold and gules (Ancestor, no. 4, p. 229; Coll. Top., vol. iv, pp. 64, 395; cf. ante, vol. v, p. 126, note "a"). When Cussans wrote, they were to be seen in windows in the church of Sawbridgeworth (Hist. of Herts, vol. i, Hundr. of Braughing, p. 97). Round, Geoffrey de Mandeville, pp. 393-96, has shewn that this coat was originally borne by Earl Geoffrey, from whom it passed to Say (if it was not used concurrently by both). Derivatives of the arms appear later in Kent, the families of de Peckham and St. Nicholas bearing over their own arms a chief quarterly gold and gules (Arch. Cant., vol. xxviii, p. 209).
(b)He is described in the foundation-narrative of Walden Abbey as "ferocis animi vir et bellicosus" (Dugdale, Mon., vol. iv, p. 142). A William de Say occurs as witness to 2 charters of Henry I, confirming gifts to the Abbey of St. Evroul, both granted at Rouen, one in 1113 (Round, Cal. Docs., no. 624; Orderic, ed. Le Prévost, vol. v, p. 199), the other between 1123 and 1128 (Idem, vol. v, p. 204); but there was a William de Say who m. Agnes, da. of Hugh de Grentemesnil, before 1098 (Idem, vol. iii, p. 361).
(c)Hen. Huntingdon (Rolls Ser.), p. 277; Chron. Abb. Rames. (Rolls Ser.), p. 347; Gesta Stephani (Rolls Ser.), p. 106; Gerv. Cant. (Rolls Ser.), vol. i, p. 128.
(d)Concedo etiam quod Willelmus de Sai habeat omnes terras et tenementa que fuerunt patris sui, et ipse et heredes sui (Round, Geoffrey de Mandeville, p. 169).
(e)See references in note "c" above.
(f)The Earl himself did not die until Sep. (Ante, vol. v, p. 116). Dr. G. Herbert Fowler, in a paper on the Beauchamps, Barons of Eaton (Beds. Hist. Rec. Soc., vol. ii, p. 61), cited a confirmation to St. Neot's Priory by William de Say and Beatrice his wife and William his heir for the soul of Earl Geoffrey de Mandeville of a grant of land in Eaton Socon, Beds. The original grant was made for the soul of the same Earl by Hugh de Beauchamp, who, Dr. Fowler says, was William's man in respect of the land (B.M. MS. Cotton, Faustina A iv, f. 54, ex inform. C. T. Clay). Eaton Socon had been restored to the Earl in 1142 by the Empress Maud, and such interest as William possessed must have been in right of his wife. The Libellus de Anniversariis of Ramsey Abbey (Dugdale, Mon., vol. ii, p. 566) says that William de Say d. 11 Jan.,

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Earl GEOFFREY abovenamed, and da. of William DE MANDEVILLE. The Earl is said to have brought her to England for the marriage.(a) She lived to a great age;(b) d. 19 Apr. in or before 1197, and was bur. at Walden Abbey.(c)
without giving the year. This refers to William de Say I, because William II d. about Aug. in 1177 (Ante, vol. v, p. 120, note "i"; Rot. de Dominabus, P.R.S., pp. 46, 49).
(a)Dugdale, Mon., vol. iv, p. 142. Through her, as heir to her father, brother and nephew (Idem, vol. iv, pp. 145, 149), after the death s.p. of her nephew William de Mandeville, Earl of Essex, in 1189, a large part of the Mandeville estates passed to the Say family (Round, Geoffrey de Mandeville, p. 243); but in the event Geoffrey FitzPiers obtained the lion’s share (Ante, vol. v, p. 126; Dugdale, Mon., vol. iv, p. 145; Pipe Roll, 2 Ric. I, p. 111 [and so in succeeding years]; Curia Regis Rolls, vol. vii, p. 110).
(b)According to the Rot. de Dominabus (P.R.S.), p. 76, she was 80 years of age in 1185.
(c)Ante, vol. v, p. 122.