At 1:30am on 28 March 1942 Roy was on the deck of , an old First World War , formerly , with her Oerlikon 20 mm cannon blazing at the German guns only a few yards away. The ship was loaded with 4.5 tons of explosives on its way to ram the dock gate in St. Nazaire port during the St Nazaire Raid, as part of Operation Chariot. The raid was described by Winston Churchill as "a deed of glory intimately involved in high strategy".