Douglas attended a naval school at age 10 and started training at sea aged 14 as a cadet. He became the youngest petty officer in the navy and at the start of WW2 he was serving on HMS Coventry, an anti-aircraft cruiser. He later served on the cruiser HMS Fiji and then the battleship King George V which was providing cover for Russian convoys. He was present when this ship and others sank the German battleship Bismarck in 1941. During this time he received news that his brother had been killed in North Africa.

By June 1944 he was chief coxswain on board HMS Prince Charles, a ship carrying eight landing craft. He, and others, were given pills to help them stay awake for 24 hours. The ship picked up US Rangers, troops he describes as ‘brilliant soldiers’, at Southampton. They then sailed to Omaha beach, disembarking the Rangers from their landing craft at 7am on D-Day. Despite heavy Allied shelling and bombing the German defences took a heavy toll on the American troops. He remembers one landing craft hitting a mine and parts of bodies being hurled through the air. At one point, during the chaos of the fighting, he jumped into the sea and turned a landing craft around to enable the troops to disembark. He described this not as conscious bravery but something he did spontaneously under the stress of the situation.

His only injury of the war was losing some teeth during a game of hockey!