Born in Ireland, O’Meara joins the British navy in 1808, after he has been dismissed from the army for assisting in a duel. In July 1815 he is serving on the HMS Bellerophon when Napoleon surrenders on board.
His knowledge of Italian impresses Napoleon and he requests O’Meara’s services on St. Helena. O’Meara remains on St. Helena as Napoleon’s personal physician until 1818, when his refusal to spy on the Emperor for the British governor of the island causes him to be dismissed from that post.
On his return to London, O’Meara publishes Napoleon in Exile, or A Voice From St. Helena (1822) a book which charges Sir Hudson Lowe with mistreating the former emperor and created no small sensation on its appearance. Less known are his secret letters he sends clandestinely from St. Helena to a clerk at the Admiralty in London. These letters shed a unique light on Napoleon’s state of mind as a captive and the causes of his complaints against Sir Hudson Lowe and the British government.
O’Meara is also the physician who performs the very first medical operation on Napoleon by extracting a wisdom tooth in the autumn of 1817.
O’Meara also becomes involved in politics, helping to found the Reform Club. O’Meara dies on June 3, 1836, from complications after catching a cold while attending one of Daniel O’Connell‘s political rallies.