HMS Portland was a 50-gun fourth-rate ship of the line of the Royal Navy.

[3] During this time, the ship spent nearly a month at Port Royal, Jamaica.

[2] The ship served during the American Revolutionary War: On 13 February, 1778 she captured sloop "Swallow" 108 Leagues south west of Anguilla.

This would result in the ship's captain, Thomas Dumaresq and flag officer Admiral James Young getting arrested by the Court of Vice-Admiralty at Antigua due to the tribunal of declaring the privateers as legal even without the proper paperwork.

This resulted in a high-profile case surrounding Captain Thomas Dumaresq of the Portland that had the First Lord of the Admiralty, John Montagu, 4th Earl of Sandwich and King George III involved.