She almost immediately became caught up in the events of the mutiny at the Nore, and was one of a few loyal ships tasked with attacking mutinous vessels if they could not be brought to order.

She moved to the Mediterranean in 1799, spending the rest of the French Revolutionary Wars in operations with Vice-Admiral Lord Keith's fleet.

After refitting, and spending time on blockades, she formed part of Lord Nelson's fleet at the Battle of Trafalgar, and was heavily involved in the fighting, sustaining casualties of 10 killed and 34 wounded.

Neptune was ordered from Deptford Dockyard on 15 February 1790, to a design developed by Surveyor of the Navy Sir John Henslow.

[4] Stanhope sailed from Woolwich on 11 June 1797, flying the broad pendant of Commodore Sir Erasmus Gower, and made for the Nore.

[3] Before they could proceed word came that the mutineers had entered negotiations with the Earl of Northesk, captain of the 64-gun HMS Monmouth, and by 9 June the mutiny was on the verge of collapse.

[3] The squadron, commanded by Rear-Admiral Sir Charles Cotton, rendezvoused with Keith's force at Menorca on 7 July, bringing the British fleet in the Mediterranean up to 31 ships.

[3] Keith intended to intercept a large Franco-Spanish force of 42 ships under Admirals Étienne Eustache Bruix and Jose Mazarredo, and set out to sea on 10 July.

With the draw down in hostilities prior to the signing of the Treaty of Amiens in March 1802, Neptune was one of the many ships of the Mediterranean fleet to be ordered home, arriving at Portsmouth on 24 February.

[2][3] With Neptune fully refitted and stored, she sailed from the dockyard and joined the Channel Fleet at Spithead on 29 October.

He was replaced by Captain Thomas Fremantle on 8 May, and was sent to join Robert Calder's force blockading Ferrol, after the Franco-Spanish fleet had arrived there after the Battle of Cape Finisterre.

'[7][8] During the battle however, Midshipman William Baddock commented that 'The old Neptune, which never was a good sailer, took it into her head that morning to sail better than I ever remember to have seen her do before.

[8] Fremantle had been promised a position second to Nelson aboard HMS Victory, and by 10 o'clock was sailing fast enough to threaten to overtake her.

[10] As she passed under Bucentaure's stern, Neptune discharged a double-shotted broadside from her larboard (port) guns, with devastating consequences on Villeneuve's already disabled flagship.

[10] Fremantle then spotted the towering mass of the Spanish four-decker Santísima Trinidad sailing away from him, and steered towards her starboard quarter in the hope of raking her stern.

[12] Neptune left the 98-gun HMS Prince to take possession and headed north to cut off the remains of the enemy fleet, briefly becoming engaged with the French 74-gun Intrépide.

[2][11] In January 1809 an attack on the French colony of Martinique, governed by Admiral Louis Thomas Villaret de Joyeuse, was planned.

Neptune became the flagship of the expedition's commander, Rear-Admiral Alexander Cochrane, and the invasion force, consisting of 44 vessels and transports for 10,000 troops under Lieutenant-General George Beckwith, sailed on 28 January.

[11] 600 troops were put ashore at Cape Solomon under Major Henderson, both landings supervised by Captain William Charles Fahie aboard the 74-gun HMS Belleisle.

[11] An additional force of 6,500 men were landed in the north of the island under Major-General Sir George Prévost, and the French were driven into several fortified positions, the last of which surrendered on 24 February 1809.

A British force under Major-General Frederick Maitland and Captain Philip Beaver in Acasta, landed troops on the islands capturing them.

[13] The Navy Board proposed that she be converted into a prison ship, a recommendation the Admiralty accepted, and she was taken in hand for fitting out on 22 November.