La Clue was attempting to evade Boscawen and bring the French Mediterranean Fleet into the Atlantic, avoiding battle if possible; he was then under orders to sail for the West Indies.

During the evening of 17 August the French fleet successfully passed through the Strait of Gibraltar, but was sighted by a British ship shortly after it entered the Atlantic.

Aware that he was pursued, La Clue altered his plan and changed course; half his ships failed to follow him in the dark, but the British did.

France supported Austria and Russia in a land campaign against Prussia, and launched what it saw as its main effort in a maritime and colonial offensive against Britain.

[5] From June it came under the control of the assertive new secretary of state for the southern department (foreign minister), William Pitt, who imposed a coordinated strategy.

However, at the best of times the French struggled to crew their full fleet with experienced mariners; landsmen could be used, but even a small deficiency in ship handling translated into a marked handicap in combat.

Three years into the war, thousands of French seamen were held as prisoners by the British; many more were engaged in speculative, and occasionally lucrative, privateering careers; and the unhealthy conditions, onerous onboard discipline and poor wages, paid late, were a strong disincentive to service.

[15] He ordered the first two of his frigates to be ready for sea to patrol to the east, where the Mediterranean narrowed to the bottleneck of the Strait of Gibraltar, to give warning if the French were to attempt to break out.

[18] After great difficulties in preparing them for sea, nine French ships of the line, under Maximin de Bompart, were despatched to relieve the island.

[19] News of this disaster was passed back to Paris, where after deliberation it was decided to reinforce Bompart's force with the Mediterranean Fleet.

Orders to sail reached its commander, Admiral Jean-François de La Clue-Sabran, at the end of July, and it left Toulon on 5 August.

[20] La Clue intended to pass the Strait of Gibraltar by night, in order to keep the British in ignorance of his absence from the Mediterranean.

[17] During the late evening of 17 August the French passed through the strait, but were observed shortly afterwards by the British frigate HMS Gibraltar.

The process of fitting, or "bending", sails to the masts of the large warships of the time was a complicated one, and most British ships were forced to do this as they got under way, in the dark, undermanned and with few officers.

[24] The French ships had all been issued with sealed orders, which they were to open on passing the Strait of Gibraltar; these instructed them that the fleet was to rendezvous at Cádiz.

So at about midnight La Clue had his flagship, Océan, light her stern lantern, turn to port (left, or westward) and reduce her speed.

The naval historian Sam Willis suggests it is possible that La Clue – who had been ordered to avoid battle at all costs – knowing the entire fleet was relatively close and not wishing to advertise his manoeuvre to the British, omitted to do this.

[26] At about 6:00 am a group of large ships came into view and La Clue remained stationary, believing them to be the missing component of his fleet.

The British ships proved to be faster, and were slightly favoured by variable winds, allowing them to gradually overhaul the French by the afternoon of 18 August.

[32][33] At 2:30 pm the British Culloden engaged the rearmost French ship, the Centaure; they were evenly matched, each being equipped with 74 heavy guns, 37 on each side.

[34] Namur passed three French ships, receiving a broadside from each; Boscawen ordered that there be no return fire, instead having his crew lie down, to minimise casualties.

[38] The naval historian Nicholas Tracey suggests La Clue sailed an incorrect course, failed to weather Cape St. Vincent, and became trapped against a lee shore.

[38] As Boscawen approached in Newark, the Portuguese opened fire and he hove to outside of cannon range and selected several ships to attack the French "without any regard to the laws of neutrality.

But by the time they evaded Brodrick during a winter storm in January 1760, the French Atlantic Fleet had been destroyed at the Battle of Quiberon Bay, and they returned to Toulon instead.

[47] Hearing the news of the victory, the notoriously nervous British prime minister, the Duke of Newcastle, said "I was afraid of invasion till now.

[55] The historian Geoffrey Blainey describes Boscawen as perhaps the most successful naval commander of the 18th century, "when inconclusive battles at sea were normal.

[note 2] Serving on board Océan as a junior officer was Pierre André de Suffren, who was later to gain fame as an admiral leading a French fleet in the Indian Ocean.

[60][61] A young slave named Olaudah Equiano, who would later become a prominent abolitionist in England, participated in the engagement on the British side.