I can’t say for certain if there were any First World War pilots that re-enlisted for combat duty during the Battle of Britain or for the Second World War, I suspect by the time of the Second World War, anyone who flew during the First was at an age where their reflexes had degraded and To a point where they couldn’t keep up with younger pilots.

That said, there were certainly First World War pilots that saw service during the Second World War, just not at the combat pilot level. By the time of the Second World War, the RAF’s senior command level was populated by officers who had served in the Royal Flying Corps. Not least among those was Keith Park. Park was a New Zealander who joined the New Zealand Expeditionary Force and served at Gallipoli. Later in the war, he was deemed unfit for further service (he was blown of his horse by an artillery shell). He joined the Royal Flying Corps, intent on continuing his war service and rose to the rank of major. He flew throughout the latter years of the war, proving himself to be an accomplished pilot. After the war, he stayed on with the Air Force, now known as the RAF and rose to the rank of Air Vice Marshal in time for the Battle of Britain. Throughout the battle, Park travelled throughout his area of command in his personal Hawker Hurricane. I mention this because it demonstrates that First World War pilots flying biplanes could indeed translate their skills and fly the single engine fighters that dominated Second World War aerial combat.

Additionally, biplanes were used almost universally by air forces as training aircraft. Though lacking the speed and manoeuvrability of more modern aircraft, biplanes were suitable for teaching the basics of throttle, pitch and yaw as well as take off and landing. It was also necessary for Second World War pilots to transition from biplanes to modern aircraft during the actual war. At the beginning of the war, the British Fleet Air Arm flew Swordfish biplanes, utilising them as torpedo attack aircraft. These planes were used to sink an Italian battleship at the Battle of Taranto and also used to attack the Bismarck. Their obsolescence however quickly became apparent when faced with modern opposition and they were withdrawn from front line combat operations and were replaced by Fairey Barracuda monoplanes, prompting the Swordfish pilots to transition to the newer aircraft.

RAF training was in several stages. Elementary Training taught prospective pilots the basics of flying from scratch; during the Second World War the most common primary trainer was the Tiger Moth biplane, not radically different from aircraft of 1918. Successful students progressed to Service Training using more advanced aircraft with flaps, retractable undercarriage etc. such as the North American Harvard for fighter pilots or Airspeed Oxford for bomber pilots. Service Training also started to introduce combat elements such as aerial gunnery. The final step was an Operational Training Unit (OTU), equipped (ideally) with the same type of aircraft that would be flown in active service (though they tended to be slightly obsolete or worn-out models), the instructors often being pilots with combat experience on rotation.

Reserves were assessed based on previous experience, amount of recent flying etc. as to whether they were ready for immediate squadron service or required a further 6, 12 or 16 weeks training. New recruits with flying experience could skip (or rapidly progress through) elements of the training programme - e.g. some of the US 'Eagle Squadron' volunteers went straight to Operational Training Units. So there was scope for a hypothetical Great War veteran to transition to Spitfires via e.g. a Service Flying Training School, but for one stumbling block - age. Combat flying was a young man's game. In his despatch on the Battle Dowding wrote "Only exceptionally should officers over 26 years of age be posted to command Fighter squadrons"; Squadron Leaders 'Sailor' Malan and Douglas Bader were unusually 'old men' at the age of 30. There were other roles for older veterans - staff officers, instructors at the various types of flying school, other administrative posts.

That said, there were a couple of Great War veterans (who had remained in the service for the duration) flying in combat during the Battle of Britain, very much the exception to the rule. Ernie Mayne (born January 1901) joined the Royal Flying Corps in 1917 and in 1940, with 74 Squadron, flew over Dunkirk and during the Battle. Stanley Vincent (born April 1897) joined the RFC in 1915 and, as Station Commander of RAF Northolt in 1940, sometimes accompanied his squadrons on missions; he was the only RAF pilot with victory claims in both wars.

An even more unusual cases was Vashon James Wheeler (born September 1898). Wheeler served in the army in the First World War (having lied about his age) and learned to fly in the inter-war period as an airline pilot before joining the RAF in 1940 (having lied about his age again, this time to reduce it). Wheeler's first role was at a Bombing and Gunnery Training School performing tasks such as towing targets for trainees. Wanting more active service he moved first to a transport squadron, then to Coastal Command's 500 Squadron flying maritime patrols. In November 1940 he joined Fighter Command flying Hurricane, Havoc, Beaufighter and Mosquito night fighters, then moved to Bomber Command in 1943 to fly Lancasters; he was shot down over Germany in 1944 aged 46.