The son of a vintner in Greyfriars, London, who was admitted to St. Paul's School, he was sent to Cadiz while still young, to be trained in commerce.
He left England in August 1788 with the intention of crossing the desert from Tripoli to Fezzan, in what is now Libya.
The plan was to collect information in Fezzan, and from traders, on the interior, and to return home by way of The Gambia or the Guinea coast.
A revolt on the intended route delayed his journey, but two sharifs offered him safe conduct.
[1] Lucas turned back ar Memoon on 20 March 1789, reaching Tripoli on 6 April, and England on 26 July.