After the death of King Edward there was a power-struggle between the Woodvilles and Richard Duke of Gloucester, who had been appointed as Protector of the under-age heir Edward V. The Woodvilles were keen to bypass the protectorate and have Prince Edward crowned quickly.
He seems to have left London to take command of the fleet shortly after Richard initiated his coup by arresting Edward's brother Anthony Woodville, 2nd Earl Rivers, at Stony Stratford.