F/O Barker was born in Bow, London. He attended Old Palace School and Coopers' Company School. He joined the RAFVR in April 1939 as an Airman u/t Wop/AG.
Called up on 1st September 1939, he joined 264 Squadron on its reformation on 30th October 1939 at Sutton Bridge, and he teamed up with Sergeant E R Thorn.

Over Dunkirk on 28th May 1940 the Defiants were attacked by Bf 109s, the enemy shot down three of the Defiants, however Thorn and Barker destroyed three Bf 109s and forced the remainder to break off the attack, the following day they succeeded in shooting down two Ju 87s and a Bf 110 followed by a He 111 on 31st May and another shared. For their determination and skill Thorn and Barker were both awarded an immediate DFM (14th June 1940) which mentioned they had accounted for six enemy aircraft. They were also both promoted to Flight Sergeant.

When 264 moved south to Hornchurch on 21st August 1940, Thorn and Barker were again in action. On the 24th, they took off from Manston and encountered Ju 88s escorted by Bf 109s and managed to destroy one of the Ju 88s. Two days later, on the 26th, operating from Hornchurch they were patrolling the Dover area and were involved in combat with a formation of 12 Do 17s and managed to destroyed two, but while attacking a third they were attacked by Bf 109s. A fire started and Thorn put the aircraft in a dive in an attempt to put out the fire, pulling out of the dive at 500 ft a Bf 109 was still on their tail, and the Defiant still on fire, fortunately a Hurricane came to their aim and between them they were able to shot the Bf 109 down. They then proceeded to abandon their aircraft and escaped with only slight injuries. For this action they were each awarded a Bar to the DFM (11.2.41).
They destroyed a He 111 at night on 9th April 1941. The partnership broke up when Thorn was posted to 32 Squadron in October 1941 having scored thirteen victories.
Barker remained with 264 until 1942, and was subsequently posted to the Middle East as an air gunnery instructor.

He was commissioned in Apri1 1944 and released from the RAF in 1946, as a Flying Officer.  It is believed that Barker is the highest scoring air gunner of the war.