Complex sentence: She is known to have been in Martinique waters in 1811, and in the spring of 1812 was carrying dispatches from Lisbon back to Great Britain when she was spotted by a flotilla of five French ships of the line that had escaped from Lorient.
Split into simpler sentences: She is known to have been in Martinique waters in 1811. In the spring of 1812 she was carrying dispatches from Lisbon back to Great Britain when she was spotted by a flotilla of five French ships of the line that had escaped from Lorient.