Gilbert was the son of Agnes de Chesney, sister of Robert de Chesney, bishop of Lincoln (1148-66), and her husband, who was possibly Robert Foliot, steward of David I (d.1153), when he was earl of Huntingdon. His mother was probably daughter of Roger de Chesney from Normandy and Alice de Langetot, daughter of Ralph de Langetot. Gilbert was related to Miles, constable of Gloucester and earl of Hereford (d.1143), both Richards de Belmeis, bishops of London (1108-27, 1152-62), and to Richard of Ilchester, bishop of Winchester. Gilbert probably studied Roman law in Bologna and theology at Exeter; he became a monk at Cluny about 1130 and soon became one of the priors. He also became prior of the Cluniac house at Abbeville and in 1139 he was abbot of St Peter at Gloucester (Benedictine). Gilbert was consecrated bishop of Hereford on 5 September 1148 at St Omer. He was transferred to the bishopric of London in March 1163 and held this position until his death, aged about eighty, on 18 February 1187.
C.N.L. Brooke, 'Gilbert Foliot', ODNB, xx, 218-21; [http://www.oxforddnb.com/view/article/9792]