In 1444, he was made premier Earl of the realm, and on 14 April 1445, was created Duke of Warwick,[2] and around the same time, granted the Forest of Feckenham.

[3] He is said to have been crowned King of the Isle of Wight in 1444[4] by Henry VI, to place his playmate on a more equal standing with him, but this story is considered unhistorical.

However, the issue was rendered moot by his death on 11 June 1446, at which time the dukedom expired for lack of heirs male.

On his death, the earldom was inherited by his two-year-old daughter, Anne (14 February 1444 – 3 June 1449[6]), suo jure Countess of Warwick.

[7] In the end, his full sister Anne (who was married to Richard Neville, eldest son of Richard Neville, Earl of Salisbury, and brother to Beauchamp's widow) was declared the heir, due to the English common law principle that "possession by the brother makes the sister the heir", which denies relatives of the half-blood from inheriting when full-blood relatives are available to inherit.