Born in Dunedin, Hesselyn joined the Royal New Zealand Air Force in 1940 and completed his flight training the following year.

Repatriated to England for a rest, he later collaborated with the Australian flying ace Virgil Brennan in the writing of Spitfires over Malta, a book about their experiences on the island.

Liberated in 1945, he formally transferred to the RAF two years later and attained the rank of squadron leader before his death in 1963 of stomach cancer, aged 42.

He declined in favour of enlisting in the Royal New Zealand Air Force (RNZAF) and was formally attested on 23 June 1940.

[8] After a period of leave, Hesselyn was posted to Britain to serve with the Royal Air Force (RAF) and departed in April aboard the ocean liner Aorangi.

[9] By July, he was in England and was on a flying refresher course, training on Miles Masters before proceeding to Hawker Hurricane fighters.

[11] Hesselyn volunteered for an overseas posting and in February 1942, he was advised that he was to be sent to Malta, where he would join the island's air defences during incessant Axis attacks.

[12] An attempt to fly off the carrier on 26 February had to be cancelled due to malfunctioning long-range fuel tanks but on 7 March he and 14 other pilots took off from the deck of Eagle and flew for 4 hours to the island.

[13][15] Hesselyn's first operational flight with the squadron was on 11 March, when he and three other Spitfire pilots and 16 Hurricanes intercepted a small bombing raid.

[17] On 1 April Hesselyn, while on patrol north of Grand Harbour, shot down a Messerschmitt Bf 109 fighter that was escorting a flying boat.

Later in the day, he was part of a group of Spitfires scrambled to intercept an incoming bombing raid and shot down a Junkers Ju 87 dive bomber.

[18][19] Availability of aircraft continued to limit Hesselyn's flying time for the first two weeks of April, and he was kept occupied with construction of air defences, but in the meantime the squadron's successes grew.

[20] On 20 April, he and another pilot were sent to provide cover for a group of Spitfires returning to the airfield after being scrambled to intercept a bombing raid.

[23] He shot down another Ju 87 over Ta Kali on 26 April but Hesselyn, leading a section of Spitfires for the first time, was attacked by Bf 109s immediately afterwards.

He has destroyed 5 enemy aircraft, 2 of which he shot down in one engagement.On 10 May, Hesselyn's was one of 20 Spitfires scrambled to intercept around 20 Ju 88s, escorted by Bf 109s, approaching Grand Harbour.

He promptly took evasive action, which saw the attacking aircraft overshoot him and enter the range of his cannons; he opened fire and destroyed the Bf 109.

[30][31] Returning to flying operations, Hesselyn shot down another Bf 109 on 12 May; this was seen to crash into the sea 20 miles (32 km) south of Malta.

[36] The award was officially announced in the London Gazette on 29 May; the published citation read: During a period of 4 days' operations in May, 1942, this airman destroyed 5 enemy aircraft bringing his victories to 10.

Although fighting at great odds in the heavy raids on Malta, Flight Sergeant Hesselyn never hesitates in his efforts to destroy the enemy.

His courage and devotion to duty are outstanding.Axis activity over Malta during the day began to drop off towards the end of the month, and this continued into June with more raids being mounted at night and fewer opportunities for the units equipped with daytime fighter aircraft, such as No.

On 22 June, leading a section of Spitfires on an aerial search and rescue mission involving escorting two Supermarine Walruses, he was credited with damaging a Focke-Wulf Fw 190 fighter.

222 Squadron was rested for a few days and did not resume operations until 2 October, when the Hornchurch Wing provided cover for Consolidated B-24 Liberators attacking a target in occupied Holland.

[51] The next day, he flew his 69th and final operation with the squadron when the Hornchurch Wing went on a Ramrod mission, acting as high cover for several B-26 Marauders heading for Beauvais.

[52][8] According to Caldwell, three Luftwaffe pilots filed claims over a Spitfire in the area of Beauvais and may have been responsible for shooting him down: Feldwebel Gerd Wiegand, Major Klaus Mietusch and Hauptmann Hermann Staiger.

His successes are a fine tribute to his great skill, courage and keenness.After his capture, Hesselyn was hospitalised at Beauvais for treatment of injuries sustained as he was shot down and was not transferred to Germany until the end of October.

They had hidden in the ceiling space of the camp theatre in the late afternoon and that night sneaked out and, avoiding sentries, scaled a gate undetected by searchlights.

[60] He attended a number of functions in his honour but did not enjoy the attention and family members noted he kept late hours, struggled to sleep, and also drank heavily.

By this time he had developed a reputation as being a difficult commander, prone to losing his temper over minor issues, and continuing to excessively consume alcohol.

[72] Hesselyn's health began to decline in April 1963 due to what was initially believed to be a stomach ulcer, but was later found to be cancer; he died at the RAF Hospital at Uxbridge on 14 November 1963, aged 42.

[74] After his death, his wife returned his medals to his parents;[73] they were later sold to an Australian collector, and in 1998 came up for sale at auction in London, where they fetched £7,200.