A new class of post ship had not been implemented by the Royal Navy for almost twenty years, and Williams' changes were minor.

[2] Vestal, the sixth ship of the class, was ordered on 1 August 1775 to be built at Plymouth Dockyard by the shipwright John Henslow.

With a crew complement of 140, the post ship held twenty 9-pounder long guns on her upper deck.

[4] Vestal was commissioned under the command of Captain James Shirley about the time of her launching, before the ship had been coppered.

[1][8] The 14-gun ship sloop HMS Pegasus also disappeared off Newfoundland in October, and was similarly thought to have been lost in a storm as she attempted to make shore.