Claude was a commissioner for the Anglo-French Treaty of Ardres, also known as the Treaty of Camp, which was signed on 7 June 1546 and a step towards the conclusion of the Italian War of 1542–1546. After a delay which the English found frustrating, Claude then visited England as a special ambassador for the peace treaty 20–30 August 1546. Four cannon at Walmer Castle burst while firing his salute. Claude wrote from London to his ally Mary of Guise in Scotland on 28 August, explaining his difficulties in forwarding their mutual interest.