Brown had learnt to fly in the University Air Squadron and on reaching Britain he volunteered for the Fleet Air Arm. His first operational appointment was the 802 Naval Air Squadron, flying the Grumman Martlet from the escort carrier Audacity, providing fighter protection to North Atlantic convoys. He was twice involved when his squadron shot several German long-range bombers, and was awarded the DSC for his bravery and skill in action against enemy aircraft and in the protection of a convoy against heavy and sustained air attacks. Audacity was torpedoed and sunk in December 1941: Brown was one of only two survivors among the aircrew.