Originally, the Admiralty had intended to order her to be built to the lines of Sir John Williams' Alfred class, specifically HMS Alexander.

Of the other eleven ships mentioned, seven had the plain white figureheads as completed by the dockyards, whilst four had painted theirs with a larger palette since being launched.

She commissioned under her first captain, John Elliot, in May 1779, while her first action came on 16 January 1780, when she fought in the Battle of Cape St Vincent as part of Admiral Sir George Rodney's fleet.

[6] In November 1781, the Admiralty had received intelligence that a large convoy was preparing to sail from Brest under Admiral de Guichen.

Edgar was part of Admiral Richard Kempenfelt's squadron of 18 ships (11 of which mounted 64 or more guns), which he commanded from HMS Victory.

Kempenfelt was ordered to intercept the convoy, which he did in the afternoon of 12 December in the Bay of Biscay, approximately 150 miles (241.4 km) south-west of Ushant.

[7] Her second major action came on 20 October 1782 when she was part of Admiral Richard Howe's fleet of 35 ships of the line at the Battle of Cape Spartel.

[11] In 1800 Edgar was part of the Channel Fleet under Admiral Sir Alan Gardner blockading the important French port of Brest.

After passing down the Outer Channel in order to negotiate the southern tip of the Middle Ground shoal off the coast from Copenhagen, Edgar was leading Vice-Admiral Horatio Nelson's line, and was the first to commence firing, as soon as she was in range of the Danish Prövesteen.

She was recommissioned in 1805 as part of the doubling and bracing programme, and served as Admiral Lord Keith's flagship off Texel, blockading the Dutch coast.

[3][9] Edgar, along with several other ships, was in the Downs on 17 December, when HMS Victory came in to shelter from gales that had blown up, hampering her progress to Chatham.

All were found guilty, despite attempts by Edgar's petty officers to prove that they had been goaded into their actions by threats from the rest of the crew.

[9] In May 1808 Edgar was one of the 12 ships of the line forming part of Vice-Admiral Sir James Saumarez's squadron sent to the Baltic after Denmark's declaration of war against Sweden.

[17][Note 2] In early July 1810 Edgar, in company with Dictator and Alonzo, sighted three Danish gunboats under the command of Lieutenant Peter Nicolay Skibsted, who had captured the Grinder in April of that year.

The gunboats (Husaren, Løberen, and Flink) sought refuge in Grenå, on eastern Jutland, where a company of soldiers and their field guns could provide cover.

However, the British mounted a cutting out expedition of some 200 men in ten ships’ boats after midnight on 7 July, capturing the three gunboats.