In 1648, when the second period of conflict flared up, Sir William became directly involved in the fighting for the first and only time, under the command of Sir John Mayney. Separated from the main loyalist forces, the detachment in Maidstone had to fight unsupported against a large force of the New Model Army, under Sir Thomas Fairfax, or Lord Fairfax of Cameron as he had just become, having inherited the family peerage from the Kingdom of Scotland.