[4] Governor Simcoe served the North West Company (NWC) fur trade on Lake Ontario from her launch at Kingston, Upper Canada, on 29 October 1793.

"On the eve of the Battle of Queenston Heights on 13 October 1812 he delivered a shipment of gunpowder to Niagara and afterwards returned to York with prisoners and the news of Major-General Sir Isaac Brock's death.

"[6] On her last merchant voyage, on 11 November 1812 Commodore Isaac Chauncey's United States Navy (USN) Lake Ontario squadron then patrolling off Kingston spotted Governor Simcoe and chased her.

Governor Simcoe "evaded capture but ran too closely over a shoal and sank at its berth in Kingston from the damage it had incurred.

As Sir Sydney Smith she took part in attacks on Sackets Harbor and Oswego, as well as engagements against the United States Navy on 10–11 August and 11 September 1813.

Along with Lord Melville and Earl of Moira, Sydney Smith bombarded the American camp there, trading fire with shore-based artillery.

Sir Sydney Smith was refitted as a brig and renamed HMS Magnet, the Admiralty not liking to name vessels after living people.

The squadron then began a blockade of Sackett's Harbor, New York, the main US naval base on Lake Ontario on 11 May, lifting it on 5 June.

Fearing capture, Hawkesworth drove Magnet ashore 10 miles (16 km) west of the mouth of the Niagara River, salvaged what munitions he could, and then set a fuse to destroy Magnet and the remaining cargo in an enormous explosion which observers said could be heard and felt at York—approximately 30 miles (48 km) across Lake Ontario.