He trained initially in Antwerp as a landscape painter and then in London as an engraver with Francesco Bartolozzi.
[1] Lambertus Antonius Claessens was born in Antwerp where he first trained as a landscape painter at the local Academy.
[1] He collaborated on some projects with the engraver Ludwig Gottlieb Portman including on a series of portraits of the leaders of the French Revolution.
He produced many reproductions of the great Dutch, Flemish, French and Italian masters.
[3] He designed and engraved illustrations for various publications and a print representing Rights of Man and of Citizens proclaimed on 31 januari 1795 at The Hague.