Oxford was imprisoned at Hammes Castle near Calais, and was attainted early in 1475. At this time his mother, the 12th Earl's widow, was forced to surrender her property to the Duke of Gloucester. In 1478 Oxford scaled the walls of Hammes and leapt into the moat, though whether this was an attempt at escape or suicide is unclear. The new king, Richard III, ordered his transfer to England on 28 October 1484, but before the transfer could be effected Oxford had escaped, having persuaded the captain of Hammes, Sir James Blount, to go with him to join the Earl of Richmond. It is said that Richmond was "ravished with joy incredible" at this event. Oxford immediately returned to Hammes to bring the garrison there to join Richmond.