[3] In 1924, he appeared before the interview board and was given a medical examination as the first steps to admission to the Royal Naval College, Dartmouth.

He was initially rejected on the grounds of deficient eyesight, but his father lodged an appeal, and had his sight examined by an eye specialist in Edinburgh, who declared that it met the Navy's standards.

[4] Mackenzie entered the Royal Naval College in January 1927, one of 51 members of the Anson Term, three of whom would not graduate in July 1930.

Mackenzie was posted to the battleship HMS Ramillies, part of the Mediterranean Fleet's 1st Battle Squadron.

He embarked for the Mediterranean on the P&O ocean liner SS Rawalpindi, on which the new fleet commander, Admiral Sir William Wordsworth Fisher, was also travelling, completing the voyage on the battleship HMS Revenge.

In addition to service on Ramillies, Mackenzie, who was promoted from officer cadet to midshipman on 1 May 1931, spent a fortnight on the aircraft carrier HMS Glorious and three months on the destroyers HMS Worcester and Achates in the summer of 1932 in order to gain familiarity with the work of various ships of the fleet.

[6] After coursework that was interrupted by an operation on his left inner ear at the Royal Naval Hospital, Chatham, the midshipmen moved on to specialist courses in gunnery, torpedo, navigation and signals at HMS Excellent, Vernon, Dryad and Mercury.

[9] Mackenzie was posted to HMS Rainbow, one of the boats of the 4th Submarine Flotilla, which was based in Hong Kong as part of the China Station.

[10] He was promoted to lieutenant, with seniority backdated to 16 October 1935,[11] and returned to England via Japan and the Trans-Canada Railway in August 1937.

Despite the brilliant flashes and considerable noise from the deck gun, there was no sign of activity on board, and shells were pumped into Morea until she started to sink.

She found the area rich with targets moving troops and supplies from Italy to Albania for what would soon be revealed to be the Italian invasion of Greece.

On 13 September, she fired two salvoes of two torpedoes each at a range of 2,000 yards (1,800 m) at a convoy of three ships escorted by destroyers; all missed.

He received orders to return to England for the "Perisher", the five-week submarine Commanding Officers Qualifying Course.

Because the Mediterranean was closed due to the war, he had to sail round the Cape of Good Hope in the MV Britannic.

[23] On the next patrol, Mackenzie attacked a three-ship convoy on 25 November, sinking the 3,150-gross-register-ton (8,900 m3) Italian cargo ship Attilio Deffenu with a torpedo.

Failing to gain a firing position, Mackenzie surfaced, overtook them, and attacked, sinking the 5,000-gross-register-ton (14,000 m3) Italian cargo ship Fedora.

Through this narrow space, in complete darkness, they pushed and dragged the bomb for a distance of some 20 feet until it could be lowered over the side.

[27]On reading the patrol report, Admiral Andrew Cunningham ordered Mackenzie to write up the incident for gallantry awards to Roberts and Gould.

The escort left to rejoin the convoy, and Mackenzie surfaced in broad daylight and sank the lighter, the Italian Pilo 210 with his deck gun.

On her tenth patrol, Mackenzie attacked the Italian armed merchant cruiser Brioni on 16 May, but she spotted the torpedoes and evaded them.

Responding to a report from a shadowing Vickers Wellington bomber of an enemy ship escorted by two destroyers, Thrasher raced to intercept them on 4 September.

Thrasher made an abortive attack on two merchant ships on 25 October, and was subjected to a severe depth charging by the two escorts, but managed to get away.

[33] On 2 April 1943, Mackenzie assumed command of the submarine HMS Tantalus, a new boat which departed the builder's yard at Barrow-in-Furness on 31 May 1943.

After a work-up patrol in the Norwegian Sea,[21] Tantalus was assigned to the 4th Submarine Flotilla, which was part of the Eastern Fleet, and based at Trincomalee, Ceylon.

The Malays were transferred to the next junk Tantalus encountered, while the other two were taken to Australia, where the Japanese soldier was handed over to the Australian Army.

On 21 November Tantalus landed a party on Merapas Island in support of Operation Rimau, but the commandos that they expected to find were not there.

[28][1] The vessels sunk were small, and at one point ten Chinese and two Japanese were picked up from a fishing boat that Tantalus sank.

The big game was sighted on 11 February 1945: the Japanese battleship-carriers Ise and Hyūga and the light cruiser Ōyodo, escorted by the destroyers Kasumi, Asashimo and Hatsushimo, bound for Japan.

The advice did not go down well, but within a few years the British boats were withdrawn, and the Royal Australian Navy acquired diesel-powered Oberon-class submarines to replace them.

[52] He established his office and that of his immediate staff in London, which he considered was necessary in order to be in immediate contact with the Admiralty, the Ministers, and the key departments.