In the time of William the Conqueror, Alan, the son of Flathald (or Flaald) obtained, by the gift of the King, the castle of Oswaldestre, with the territory adjoining, which belonged to Meredith, Prince of Powys as Bleddyn, King of Powys. This Alan, having married the daughter and heir of Warine, Sheriff of Shropshire, had, in her right, the Barony of Warine and was s. by his son, William FitzAlan. [Sir Bernard Burke, Dormant, Abeyant, Forfeited, and Extinct Peerages,Ltd., London, 1883, p 200, Fitz-Alan, Earls of Arundel, Barons Maltravers].
Received from Henry I, extensive fiefs in Salop and Norfolk. (Ren Neville, Ancestry.com)
Alan obtained soon after the Norman conquest, a grant of the castle of Oswestry. (The Complete Peerage, vol V, pp 391-392)