Maurice de Berkeley 1243 and, on 14 December 1243, he had livery of his father's lands. He fought in the war in North Wales and in 1264 he joined the Barons against King Henry III. Berkeley died on 4 April 1281 and was buried in St Augustine's Abbey in Bristol. Maurice de Berkeley Sir Maurice de Berkeley "the Resolute" (1218 - 4 April 1281), 5th (feudal) Baron de Berkeley, was an English soldier and rebel, residing at Berkeley Castle in the English county of Gloucestershire. Maurice was born in 1218 to Thomas de Berkeley and Joan de Somery. He married Isabel FitzRoy, the
Margaret Mortimer, Baroness Berkeley Margaret Mortimer, Baroness Berkeley Margaret Mortimer, Baroness Berkeley (2 May 1304 – 5 May 1337) was the wife of Thomas de Berkeley, 3rd Baron Berkeley. She was the eldest daughter of Roger Mortimer, 1st Earl of March, the "de facto" ruler of England from 1327 to 1330, and his wife Joan de Geneville, Baroness Geneville. Margaret Mortimer was the eldest of the twelve children of Roger Mortimer, 1st Earl of March and Joan de Geneville, Baroness Geneville. Her paternal grandparents were Edmund Mortimer, 2nd Baron Mortimer and Margaret de Fiennes. Her maternal grandparents were Piers de Geneville, of Trim Castle