Sir John Le Couteur wrote in his diary on 30 April 1700: "Spoke to Mr Philippe Jean, the miniature painter, and found he would assist Mr Le Hardy's son in his line, if he came to Town". And on 7 May: "Called on Mr Jean, and carried him Mr Le Hardy's drawings. He promised he would assist in bringing him forward".
Le Hardy evidently went to London, and in 1793 he exhibited in the Royal Academy a portrait of a boy. Between that year and 1807 he exhibtied 21 miniatures in the Royal Academy and four with the Society of Artists.
Among the celebrities whom he painted were Philippe d'Auvergne, Duc de Bouillon, Dr Dumaresq, Ignaz Pleyel, the composer, Johan Salomon, the violinist, William Barrymore, the actor, Sir Henry Gould, the judge, Dr Osborn, the accoucheur, Edward Miller, the organist, John Moody, the actor, and Wilhelm Gramer, the violinist.
A miniature by him of Capt J Fiott is in the Société Jersiaise art gallery. Engravings were sold of many of his paintings, most of which were engraved by himself. Long says in his British Miniaturists:
- "Le Hardy's style varied considerably. His miniatures are well drawn, and express a good deal of character.. Some are soft in, treatment, others bolder; some somewhat French in manner, others more English".
Pasquin's Critical Guide to the Royal Academy of 1796 calls his miniature of Samuel Arnold, Organist of Westminster Abbey, "a good smiling likeness. This eminent composer looks as if in the act of letting off a pun".
Two of his miniatures are still exhibited in the Victoria and Albert Museum — The Rev A K Thomas DD and A Youth, and the latter is reproduced as one of the illustrations in the catalogue. He did not confine himself to miniatures. The National Portrait Gallery has a portrait by him of Horne Tooke the agitator, measuring 29 inches by 24.
Le Hardy's portrait was painted by Dahl and engraved by Faber. In 1802 a J Le Hardy, probably his younger brother Jean (1776- ), shared his studio, and exhibited miniatures in the Royal Academy until 1807.