[citation needed] In August 1412 Oxford was among those who sailed to Normandy under Thomas of Lancaster, 1st Duke of Clarence, to aid the Armagnac party against the Burgundians.

[4] Another member of the Duke of Clarence's expedition was Richard, 3rd Earl of Cambridge, and three years later, on 5 August 1415, Oxford was among the peers at the trial, presided over by the Duke of Clarence, which condemned to death Cambridge and Lord Scrope for their part in the Southampton Plot on the eve of Henry V's invasion of France.

[6] In May 1416 Oxford was invested with the Order of the Garter, and in that year sailed with the fleet to relieve Harfleur, taking part in the naval battle at the mouth of the Seine on 15 August.

He and his wife, Countess Alice, presented to the churches of Badlesmere, Kent, 1421, Aston Sandford, Buckinghamshire, 1422, and St Erme, Cornwall, 1432.

In October 1421 he was brought before a court consisting of the Regent, Beaufort, the Chancellor, Treasurer, Privy Seal, Justices of either Bench, and others of the council, and acknowledged that he had married the widowed Countess of Oxford without the king's permission.