The Berkeley estate had been entailed in 1349, which meant that on the death of his uncle in 1417 it should have descended to James as heir male, but Thomas had apparently not made this clear to the Beauchamps.

The Warwicks took their opportunity and had Berkeley Castle and its estate granted to three of the earl's retainers, while they tried to establish their right in law.

[4] This initial dispute lasted until 1421, when James took legal possession of his inheritance and received his first summons to parliament.

[6] During the increasingly violent dispute, Margaret captured James's wife Isabel and imprisoned her in Gloucester castle, where she died in September 1452.

[8] In 1414 his uncle similarly agreed for 600 marks that James should marry one of the daughters of Sir Humphrey Stafford of Hooke, Dorset.