When released on surrender of his castles, the earl launched a rebellion that lasted over a year.

Nonetheless, when he died in 1166, his body was taken to Walden Priory for burial despite a suggestion that his mother Rohese de Vere, Countess of Essex, send her men to seize her son's body and have it buried in the monastery she had founded at Chicksands.

The earldom of Essex eventually passed to the husband of a distant cousin of earl William, Geoffrey fitz Peter, along with the patronage of Walden and the Mandeville lands and titles.

The abbey eventually came under the patronage of the Duchy of Lancaster in the later Middle Ages, and thus passed to the crown in 1399.

The current Jacobean mansion was built for his grandson, Thomas Howard, 1st Earl of Suffolk, however.