Still too young to join the Royal New Zealand Air Force (RNZAF) when he left school, he took occasional flying lessons at the Canterbury Aero Club and also studied navigation.

[7] He departed New Zealand on 27 February aboard the ocean liner Awatea, headed for Canada and then the United Kingdom to serve with the Royal Air Force (RAF).

[8] He arrived at Uxbridge on 2 May and was subsequently posted to Coastal Command, commencing his operational training at Andover on Bristol Blenheim light bombers.

Paired with Bert Paige, an observer, and Horace Roe, a gunner, he flew his first operation on 15 August, searching for rescue dinghies in the North Sea with two other Blenheims.

[14] One of his earliest sorties with the Hudson, carried out on the night of 29 January 1942, was a patrol to seek out German shipping near Heligoland, during which Ensor sighted and attacked a convoy of three vessels.

Shutting down the engine with damaged propellers, he made for the squadron's base back in England but inadvertently flew into Holland due to a faulty compass.

Discovering his error, he dropped to low level for the return flight across Holland with his navigator, Bertram Paige, calling out approaching obstacles before increasing his height as they crossed the North Sea.

Whilst taking violent evasive action at an extremely low altitude, the aircraft struck a rock which disabled the starboard engine, rendered all instruments and the turret unserviceable, and extinguished all the lights.

Thus handicapped, Pilot Officer Ensor skilfully regained height in a heavy snowstorm but later, whilst flying over land and uncertain of his bearings, his aircraft was subjected to antiaircraft fire and searchlight activity for some 30 minutes.

Eventually, the position was identified and, ably assisted by Sergeant Paige's excellent navigation, Pilot Officer Ensor flew across the sea with only one engine of his aircraft functioning.

On reaching this country he was compelled to attempt a forced landing owing to shortage of petrol and, although it was snowing heavily, assisted by Sergeant Paige, who fired Verey lights in quick succession in an endeavour to illuminate the surroundings.

500 Squadron shifted north to Stornoway in the Outer Hebrides, where it was tasked with patrolling the regions around the Shetland and Faeroe Islands, through which U-boats would pass as they travelled from their bases in Germany to the Atlantic.

All four of the depth charges carried by his Hudson were dropped and Ensor believed the submarine had at least been damaged due to a visible oil patch left after the U-boat submerged although this was not the case.

Having worked out more suitable tactics for attacking U-boats following his experience of 27 April, this time his approach was superior with depth charges being dropped on either side of the submarine.

He believed a direct hit had been achieved with at least one depth charge, observing a large oil patch after the submarine made a steep dive.

[23][24][25] In early November the squadron was transferred to the Mediterranean and, stationed at Gibraltar and then Tafraoui, was involved in Operation Torch; the Allied invasion of French North Africa.

He made further attacks using his machine-guns which killed some of the submarine's crew but had to abandon his efforts when the Hudson ran low on ammunition, allowing the U-boat to escape.

Although the U-boat was sunk, the resulting shock wave caused significant damage to the Hudson as it passed overhead; Ensor was briefly knocked unconscious but recovered in time to bring the aircraft under control.

The Hudson's flying performance was severely compromised as both wing tips were bent at near right angles, the elevator tabs on the tailplane had been lost and the rudders were only just functional.

[27][28] For this exploit, which was described in the Official History of New Zealanders serving with the RAF as "the most spectacular U–boat attack of the whole war",[29] he was awarded the Distinguished Service Order (DSO) on 16 February 1943.

The published citation read: In November, 1942, Squadron Leader Ensor and Sergeant Roe were captain and rear gunner of an aircraft employed on an anti-submarine patrol.

Squadron Leader Ensor made great efforts to retain control but, although he succeeded in climbing to 1,500 feet, 1 engine failed and he was compelled to give orders for the aircraft to be abandoned.

Once there, at the request of Air Vice-Marshal Philip Joubert de la Ferté, he was instead posted as a staff officer to the headquarters of Coastal Command at Eastbury Park as an acting squadron leader.

It transpired that it was the Minerve, a Free French submarine, which had strayed off course; Ensor was exonerated of any blame, the captain acknowledging that he had disobeyed orders to surface in daylight.

[35] From January to May 1944, Ensor flew a total of ten sorties, one of which was an unsuccessful patrol to detect a Japanese submarine that was making its way to a German U-boat base in the Bay of Biscay.

[46] Ultimately, Ensor decided that opportunities in the postwar RNZAF would be limited and his senior officers, particularly Air Vice Marshal Sturley Simpson, the commander of No.

[52] His initial flying duties involved ferrying freight and passengers to the Mediterranean, Middle East and Asia but from June, the squadron was assigned to the Berlin Airlift.

[53] Over the next nine months, Ensor went on to fly a total of 200 sorties, from Wunstorf, in the British-controlled region of Germany, to Gatow in West Berlin, transporting food and coal.

He was promoted to wing commander at the end of the year although he was growing increasingly dissatisfied with his RAF career, due to the relatively little flying time he was able to achieve.

[66][67] In May 1957, Ensor was posted to Strubby for several weeks to undertake a conversion course on jet fighters, flying Gloster Meteors, before going on to more advanced training at Manby on Hawker Hunters and English Electric Canberras.