In early 1939 Cock was posted to No 87 Squadron at Debden, travelling to France with the squadron when war was declared.
On 10 May 1940 he claimed a Ju 88 destroyed and a Do 17 and a Bf 110 damaged, on the 12th a He 111 destroyed, a Bf 109 on the 14th, possibly a Ju 88 on the 16th, a Ju 87 destroyed and another damaged on the 18th and a Hs126 shared on the 19th.
The squadron was withdrawn to Debden and quickly moved to Church Fenton to refit. Early in July there was a further move, this time to Exeter.
Soon after midnight on the 26th Cock shot down a He 111, which fell at Smeatharpe, near Honiton. On 11 August he shot down a Ju 88 and a Bf 109 and probably shot down a Bf 110 and another Ju 88. In this engagement Cock’s Hurricane was hit by a Bf 109 and he baled out, slightly wounded. A Bf 109 fired at him under his parachute, but was shot down by Pilot Officer Dennis David of 87. Cock landed in the sea off Portland Bill, swam ashore at Chesil Beach and was taken to hospital.
Cock rejoined 87 on 11 September. On the 26th he claimed a Ju 88 destroyed and a Bf 109 damaged, on the 30th a Ju 88 destroyed and probably a Bf 109 and on 10 October he claimed another probable Bf 109.
After his engine cut out on patrol on October 24, Cock was unable to avoid colliding with Pilot Officer D T Jay. Cock made a forced-landing but Jay was killed while attempting to bale out.
Cock suffered shock as a result of this accident and spent some time non-effective sick. He was awarded the DFC on 25 October and became an instructor and then a Flight Commander on No 453 Squadron.
After a spell in Australia, Cock returned to the UK and did a tour with No 3 Squadron in France, flying Tempests. He was released from the RAF in February 1948, as a Squadron Leader. Later he was, for a time, the secretary of what was then the Australian Division of the Battle of Britain Fighter Association.
In 1983 he was in Dorset to witness the wreckage of his Hurricane, shot down on 11 August 1940, being lifted from the sea. He died in Australia in 1988.
