Bernardi is best known for his involvement in an assassination plot against William III, and his subsequent forty-year imprisonment, without proper trial, in Newgate prison.
[3] Around 1695 Bernardi began frequenting coffee-houses in London, where he came into contact with a variety of other Jacobite figures including his former commanding officer Sir John Fenwick and Ambrose Rookwood.
Bernardi was later to claim that he was unaware of the plot and was only in Rookwood's company by chance when he was arrested, although his name had in fact been included in a prior government proclamation suggesting that the authorities had good information on his involvement.
They were, however, never brought to trial and never released, with Bernardi, said to be the last surviving conspirator, eventually dying at the age of eighty after nearly forty years' imprisonment.
Bernardi and the other conspirators at Newgate were anonymously depicted, in complimentary terms, in the 1717 pamphlet The History of the Pressyard, supposedly written by an imprisoned participant in the Jacobite rising of 1715.
[5] Amongst other scenes "Mr. B[lackbour]n" and "the Major" (Bernardi) are shown earnestly discussing the tactical implications of the Battle of Preston, using a map drawn by Blackbourn.