P/O Stewart was born in Wellington on 22nd November 1916.

Charles applied for an RNZAF short commission in March 1939, and was accepted in June.
On 7th June 1940, he sailed for the UK in the RMS 'Rangitata', and was posted to 7 OTU on 4th August.
Charles joined 54 Squadron on 22nd August after converting to Spitfires.

On 24th August, Charles was shot down in Spitfire (P9389) by Bf 109s off Dover. He baled out at 20,000 feet, opened his parachute at 10,000 feet, and went into the Channel. An Air Sea Rescue launch failed to spot him on a sweep but he was picked up by another 45 minutes later. As the launch neared Dover harbour it was strafed by a Bf 109, but no damage was sustained.
Charles spent time in Canterbury Hospital, and was in the next bed to Michael Shand, also of 54 Squadron.
After rejoining 54 Squadron on 3rd September, Charles was posted to 222 Squadron at Hornchurch on 1st October. He was with the squadron for over five months and took part in ninety operational sorties.

On 12th March 1941, Charles joined the newly-formed 485 Squadron.
On 8th July, Charles destroyed a Bf 109.
On 11th July, Charles was one of eleven Spitfires on an offensive patrol. In the vicinity of Gravelines at 23,000 feet, they were attacked by six Bf 109s.
In the ensuing engagement, Charles was seen in combat, but he did not return to base. A search by the squadron in the Straits of Dover was unsuccessful.