452 Squadron in April 1941, he flew intensively on sorties to German-occupied France during the Circus offensive, during which he destroyed a number of German aircraft.

In March 1943, he failed to return from a sortie to intercept Japanese bombers attacking Darwin and was presumed to have been killed.

[1][2][3] In his fourth year of university studies at the time, Thorold-Smith joined the Royal Australian Air Force (RAAF) on 21 May 1940 as an aircraftman.

Having gained his wings, he was commissioned as a pilot officer in January 1941 and was sent to the United Kingdom to serve in the aerial campaign there.

[7][8] On 9 August, Thorold-Smith, along with future flying ace Pilot Officer Keith Truscott, shared in the destruction of a Messerschmitt Bf 109 fighter, during a sortie escorting bombers attacking a power station at Béthune.

[9][10] However, the Australian military aviation historian Anthony Cooper notes that there is a possibility that this may have been an instance of a misidentified Spitfire.

[9][14] Flying to the east of Hardelot on 13 October while acting as close escorts for some Blenheims targeting Arques, No.

On the return flight to England, he helped direct an Air Search Rescue vessel to the location of an Australian pilot who had baled out into the English Channel.

[9][15][16] As a result of an injury to Finucane, arising from an accident while drinking to celebrate the squadron's success of 18 September, Thorold-Smith was promoted to flight lieutenant and given command of one of No.

[18] In recognition of his successes over the previous few months, in early December Thorold-Smith was awarded the Distinguished Flying Cross.

1 Fighter Wing, it was tasked with the defence of Darwin from Japanese air attacks, the city having been bombed several times in the preceding year.

[2] The squadron saw little action initially but on 3 March, Thorold-Smith led a section of Spitfires in an unsuccessful pursuit of Japanese Mitsubishi A6M Zero fighters that had strafed a nearby airfield.

Thorold-Smith, along with four other pilots, had participated in night-time flying practice the previous evening and spent the night at Darwin.

A Spitfire believed to be his was seen going into the sea off Darwin Harbour but despite a search, no trace of him was found and he was subsequently reported as being missing in action.

[29][30] Thorold-Smith, having no known grave, is commemorated on the Northern Territory Memorial to the Missing at the Adelaide River War Cemetery and on the Manly Cenotaph.

[2][3] At the time of his death, he was credited with having shot down seven German aircraft, one of which being shared with another pilot, and one damaged.