Born in Surrey on 6 December 1917, McMullen joined the RAF on a short service commission in May 1937. He became a staff pilot, but joined No 54 Squadron at Hornchurch on 8 September 1939.
Over Dunkirk on 24 May 1940, he probably destroyed a Bf 109 and shared another, on the 25th he probably destroyed two Bf 110s, on the 26th he destroyed a Bf 110 and on the 28th he shared in the destruction of a Do 17.
On 4 July, McMullen’s Spitfire was damaged by Bf 109s in an engagement near Manston, and three days later he made a forced-landing at Manston after a combat with Bf 109s near Deal. On 24 July McMullen claimed a Bf 109 destroyed and probably another, on 15 August a Bf 109 probably destroyed and another damaged, on the 16th a Bf 109 destroyed, on the 18th a Bf 110 probably destroyed and a Bf 109 and a Do 17 damaged, on the 24th and 26th two Bf 109s destroyed, on the 30th a Do 17 shared, on the 31st a probable Do 17 shared, on 2 September a Do 17 destroyed and probably a Bf 109 and on the 3rd a probable Bf 110.
On 11 September McMullen moved to No 222 Squadron at Hornchurch. He claimed a Bf 109 destroyed on the 14th, a Bf 109 destroyed and a Bf 110 damaged on the 15th, a Bf 109 shared on 15 October, another destroyed on the 17th, a Bf 110 shared on the 20th, a Bf 109 destroyed and another damaged on the 25th, another destroyed and one damaged on the 28th and another Bf 109 destroyed on 8 November. McMullen’s outstanding record was recognised by the award of the DFC on 1 October.
On 23 November he was posted to No 151 Squadron at Wittering, as an Acting Flight Lieutenant and ‘B’ Flight Commander. In January 1941 he probably destroyed a Ju 88 at night. The squadron converted to Defiants and McMullen teamed up with Sergeant Fairweather as his air gunner. In April and May they shot down two He 111s and a Ju 88.
In July, McMullen was posted to No 266 Squadron at Wittering. On 19 August he shared a He 111, on the 21st damaged one, on 12 September probably destroyed another, on 13 October destroyed a Bf 109 and damaged another and on the 25th destroyed a Bf 110. McMullen was awarded a Bar to the DFC (March 1941) and a second Bar (December that year).
In late November 1941 he was posted to an OTU, as an instructor. After service at another OTU McMullen returned to operations in April 1942 and was briefly attached to No 602 Squadron before joining No 124 Squadron at Gravesend. He damaged two FW 190s on 24 May.
In June 1942 McMullen was posted to No 64 Squadron as a supernumerary Squadron Leader. He was given command of No 65 Squadron at Gravesend in July and over Dieppe on August 19, at the time of Operation Jubilee, the ill-fated raid on the French port, he damaged a Do 217. McMullen left the squadron in September and in November he briefly led No 324 Wing in North Africa before going to a staff job.
McMullen retired from the RAF on 16 December 1957, as a Squadron Leader, retaining the rank of Wing Commander. He died on 1 July 1985. His portrait was drawn by Cuthbert Orde.
