From February 1943 until July 1945, Sinclair served on the escort carrier HMS "Trumpeter". "Trumpeter" served in European waters, her duties included escorting convoys to the Soviet Union. With the end of the war in Europe, the ship was reassigned to the Far East and arrived in Colombo in July 1945. "Trumpeter" was one of the ships assigned to take part in Operation Zipper, the recapture of Malaya, but the ending of the war meant only a small part of the planned attack was carried out.