He [Waltheof] married, in 1070, Judith, daughter of Lambert, COUNT OF LENS, by Adelaide or Adeliz, sister of the Conqueror. He died as aforesaid, 31 May 1076, and a fortnight later the Abbot Ulfketel, at Judith's request and by the King's permission, removed his body to Crowland, where it was honourably entombed.(g) His widow, who as "Judith the Countess" is recorded in Domesday Book to have held estates in many counties in 1086, most of them apparently gifts from the King, her uncle, held Huntingdon in dower. She founded the Nunnery of Elstow, near Bedford. [Complete Peerage VI:638-40, (transcribed by Dave Utzinger)]
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After the execution of Waltheof, Earl of Huntingdon, King William offered Judith, his niece, the deceased earl's widow, in marriage to Simon St. Liz, a noble Norman, but the lady peremptorily rejected the alliance, owing, Dugdale says, to St. Liz's halting in one leg, which refusal so displeased the Conqueror that he immediately seized upon the castle and honour of Huntingdon, which the countess held in dower, exposing herself and her dau. to a state of privation and obscurity in the Isle of Ely and other places, while he bestowed upon the said Simon St. Liz the town of Northampton and the whole hundred of Falkeley, then valued at £40 per annum, to provide shoes for his horses. St. Liz thus disappointed in obtaining the hand of the Countess of Huntingdon, made his addresses with greater success to her elder dau., the Lady Maud, who became his wife, when William conferred upon the said Simon de St. Liz, the Earldoms of Huntingdon and Northampton. [Sir Bernard Burke, Dormant, Abeyant, Forfeited, and Extinct Peerages, Burke's Peerage, Ltd., London, 1883, p. 467-8, St. Liz, Earls of Huntingdon]
NOTE: The parentage of Judith of Lens has come under critical study since the early 1970's, when Enguerrand II was thought by some to be her father. The currently acceptable parentage among most scholars is as stated, i.e., Lambert of Boulogne. [Roderick W. Stuart, Royalty for Commoners, 3rd ed., Genealogical Publishing Company, Baltimore MD, 1998]