1921—1942

Aged seventeen, he signed up on a short-service commission with the Royal Air Force in August 1939. The first aircraft he flew was the Tiger Moth at Desford airfield in Leicestershire, after successfully completing the course he then went on to fly the North American Harvard at RAF Little Rissington with 6FTS.

He was then posted directly in May 1940 to 92 Squadron, flying Spitfires. He saw extensive action during the Battle of Britain. His first Commanding Officer was Roger Bushell, (later immortalised in The Great Escape), and his close colleagues included Brian Kingcome

He claimed a Heinkel He 111 shot down on 11 September, and a quarter share in a Junkers Ju 88 downed on 27 September 1940. Two (and one shared) Bf 109's were claimed 'damaged' during November 1940. A Bf 109 was claimed shot down on 9 July 1941 over France.

In February 1942 he was transferred to 65 Squadron based at Debden, being appointed to Flight Commander in March 1942.

On 11 August 1942, Wellum led 8 Spitfires launched from the carrier to reinforce the fighter complement to Luqa airfield on Malta. Here he joined 1435 Squadron on air defence duties before being rested after a severe bout of sinusitis.

1943—1961

Wellum suffered severe combat fatigue after three years' intensive flying, because of the immense strain that frontline British fighter pilots were put under during that period. He returned from Malta to Britain, becoming a test pilot on the Hawker Typhoon, based at Gloster Aircraft.

He finished the war as a gunnery instructor, staying in the RAF, first as a staff officer in West Germany, followed by a four year tour with 192 Squadron. He married his wartime girlfriend and had three children.

1961—

Wellum left the Royal Air Force in 1961, working with a firm of commodity brokers in the City of London, set up his own business, and then retired to Mullion, Cornwall. He had written a memoir of his time as a Spitfire pilot but never intended it for publication. However in 2000 he gave it to a young author called James Holland, who showed it to friends at Penguin, and they immediately decided to publish it.

Wellum wrote a widely acclaimed book about his experiences during World War II, entitled The Story of the Boy Who Became a Man in the War-Torn Skies Above Britain. New York: Viking Books, 2002 (hardcover, ISBN 0-670-91248-4); Hoboken, NJ: Wiley & Sons, 2003 (hardcover, ISBN 0-471-42627-X); London: Penguin Books, 2003 (paperback, ISBN 0-14-100814-8).

Wellum has contributed to various TV documentaries on the Battle of Britain, including Spitfire Ace produced by RDF Media/Channel 4 (2004) and Dangerous Adventures for Boys produced by Channel 5 (2008).

To mark the 70th anniversary of the Battle of Britain, the BBC commissioned a one-off drama for TV called First Light, based on Wellum's book of the same name. The film was first shown by the BBC on 14 September 2010. .