Neil joined the RAFVR on 17 October 1938 at the age of 18 and was called up to full-time service at the outbreak of War. He was posted to No. 8 Flying Training School on 1 December 1939 and was commissioned as a pilot officer on completion of the course. He was posted on 15 May 1940 to No. 249 Squadron RAF, which was an operational fighter squadron based at RAF Church Fenton in which he flew Hurricanes from RAF North Weald during the Battle of Britain. The enemy aircraft he destroyed with the squadron included six Messerschmitt Bf 109s, two Heinkel He 111s, a Messerschmitt Bf 110, a Junkers Ju 87, a Junkers Ju 88 and a Dornier Do 17.

Neil flew 141 combat missions during the Battle of Britain but his only serious mishap was on 7 November 1940 when he had a mid-air collision with another Hurricane and lost the rear section of his aircraft. This rendered it uncontrollable, but he managed to bail out and survived with a minor leg injury.

Neil was awarded the Distinguished Flying Cross on 8 October 1940 and was awarded a Bar to the award on 26 November 1940. He embarked with No. 249 Squadron on HMS Furious on 10 May 1941 and sailed for Gibraltar, and on arrival the squadron transferred to Ark Royal. The squadron flew to Ta' Qali on 21 May to take part in the Battle of Malta and he shot down a Macchi C.200 fighter on 12 June 1941.

On 26 December 1941 Neil left Malta and in 1942 he became tactics officer for No. 81 Group, then he served with No. 56 Operational Training Unit and was officer commanding No. 41 Squadron. He then became liaison officer to the US 9th Air Force's 100th Fighter Wing. This posting led to the award of the Bronze Star Medal. He was awarded the Air Force Cross in the 1950s and retired from the RAF with the rank of wing commander in 1964.