In autumn 1943, on the death of the incumbent, Sir Dudley Pound, Cunningham was promoted to First Sea Lord, the professional head of the Royal Navy, a position he held until his retirement in 1946.

After his retirement, Cunningham enjoyed several ceremonial positions, including Lord High Steward at the coronation of Queen Elizabeth II in 1953.

This operation was intended to find and destroy the Goeben and the Breslau but the German warships evaded the British fleet,[14] and passed through the Dardanelles to reach Constantinople.

[14] Although a bloodless "battle", the failure of the British pursuit had enormous political and military ramifications; in the words of Winston Churchill, they brought "more slaughter, more misery and more ruin than has ever before been borne within the compass of a ship.

Cunningham was impressed by Cowan's methods, specifically his navigation of the potentially dangerous seas, with thick fog and minefields threatening the fleet.

[24] Throughout several potentially problematic encounters with German forces trying to undermine the Latvian independence movement, Cunningham exhibited "good self control and judgement".

Cowan was quoted as saying "Commander Cunningham has on one occasion after another acted with unfailing promptitude and decision, and has proved himself an Officer of exceptional valour and unerring resolution.

[29] Cunningham renewed his association with Vice Admiral Cowan between 1926 and 1928, when Cunningham was flag captain and chief staff officer to Cowan while serving on the North America and West Indies Squadron, based at the Royal Naval Dockyard in the Imperial fortress colony of Bermuda, with shore headquarters at Admiralty House in Pembroke.

[30] The late 1920s found Cunningham back in the UK participating in courses at the Army's Senior Officers' School at Sheerness, as well as at the Imperial Defence College.

Having hoisted his flag in the light cruiser Coventry, Cunningham used his time to practise fleet handling for which he was to receive much praise in the Second World War.

However, a year later due to the illness of Sir Geoffrey Blake, Cunningham assumed the combined appointment of commander of the Battlecruiser Squadron and second-in-command of the Mediterranean Fleet, with HMS Hood as his flagship.

These convoys were highly significant in that they were desperately needed to keep Malta, a small British colony and naval base, in the war.

Stationed at the time at Alexandria, Cunningham entered into delicate negotiations with Godfroy to ensure his fleet, which consisted of the battleship Lorraine, four cruisers, three destroyers and a submarine, posed no threat.

The deadline was overrun but negotiations ended well, after Cunningham put them on a more personal level and had the British ships appeal to their French opposite numbers.

Although the Royal Navy had won in several actions in the Mediterranean, considerably upsetting the balance of power, the Italians who were following the theory of a fleet in being had left their ships in harbour.

Cunningham said of the victory: "Taranto, and the night of 11–12 November 1940, should be remembered for ever as having shown once and for all that in the Fleet Air Arm the Navy has its most devastating weapon.

After seeing aerial reconnaissance photographs the next day which showed several Italian ships sunk or out of action, Cunningham replied with the two-letter code group which signified, "Manoeuvre well executed".

Although Italian intentions were unclear, Cunningham's staff believed an attack upon British troop convoys was likely and orders were issued to spoil the enemy plan and, if possible, intercept their fleet.

Cunningham wished, however, to disguise his own activity and arranged for a game of golf and a fictitious evening gathering to mislead enemy agents (he was, in fact, overheard by the local Japanese Consul).

A hit on the Vittorio Veneto slowed her temporarily[48] and Iachino, realising his fleet was vulnerable without air cover, ordered his forces to retire.

In a pivotal[46] moment in naval warfare during the Second World War, the battleships Barham, Valiant and Warspite opened fire on two Italian cruisers at only 3,800 yards (3.5 km), destroying them in only five minutes.

[45] Although the Vittorio Veneto escaped from the battle by returning to Taranto, there were many accolades given to Cunningham for continuing the pursuit at night, against the advice of his staff.

[46] The defeats at Taranto and Cape Matapan meant that the Italian Navy did not intervene[49] in the heavily contested evacuations of Greece and Crete, later in 1941.

[52] Cunningham became a Knight Grand Cross of the Order of the Bath (GCB), "in recognition of the recent successful combined operations in the Middle East", in March 1941[53] and was created a baronet, of Bishop's Waltham in the County of Southampton, in July 1942.

He remains in my opinion at the top of my subordinates in absolute selflessness, energy, devotion to duty, knowledge of his task, and in understanding of the requirements of allied operations.

[59] In the position of First Sea Lord, and as a member of the Chiefs of Staff committee, Cunningham was responsible for the overall strategic direction of the navy for the remainder of the war.

He attended the major conferences at Cairo, Tehran, Yalta and Potsdam,[57] at which the Allies discussed future strategy, including the invasion of Normandy and the deployment of a British fleet to the Pacific Ocean.

With the election of Clement Attlee as British Prime Minister in 1945, and the implementation of his Post-war consensus, there was a large reduction in the Defence Budget.

[68] He attended the House of Lords irregularly and occasionally lent his name to press statements about the Royal Navy, particularly those relating to Admiral Dudley North, who had been relieved of his command of Gibraltar in 1940.

[71] Throughout this time Cunningham and his wife entertained family and friends, including his own great nephew, Jock Slater, in their extensive gardens.