She was commissioned for service under her first captain, Sir James Wallace in June 1790. She sailed to Plymouth where in August she underwent another refit, for £6,456, to prepare her for service in the English Channel. After her initial period of service she was paid off in September 1791, and underwent a more significant refit for the sum of £11,413, followed by further work being carried out the next year. She returned to service and was recommissioned under Captain Charles Boyles in July 1793. "Swiftsure" served as the flagship of Rear-Admiral Sir Robert Kingsmill, and operated on the Irish Station during 1794.