Lord Mitford.
From AWTP "Preachers, Farmers, Tinkers, and Kings" Jennifer Reeder (j-reeder@@comcast.net):
"His [William FitzWilliam`s] son, Sir Thomas FitzWilliam, had a grant of free warren, market and fair at Emley in 1253, the first mention of Emley in connection with the family.
Source cite: Complete Peerage V:518-9 Note.
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Sir Thomas Fitz-William m. Agnes, one of the daus. and co-heirs of Roger Bertram, feudal lord of Mitford, by whom he had three sons, William, his successor; Sir Roger, who had the lands of Woodhall from his father; and Peter, who was settled at Deney. He had, besides, five daughters, Margaret, Agnes, Bertha, Rometa, and Alberda, m. Sir Richard Walleis, Knt., of Burgh Walleis. Sir Thomas Fitz-William was s. by his eldest son, Sir William Fitz-William."
Source cite: Sir Bernard Burke, Dormant, Abeyant, Forfeited and Extinct Peerages, Burke`s Peerage, Ltd., London, 1883, p. 215, Fitz-William, Baron Fitz-William.