Barry O'Meara was the Navy surgeon chosen by Napoleon in July 1815 to follow him to St. Helena as his personal physician. O'Meara's unique position among the captives gave him an insight into their personal routines and thoughts. His status as a British officer gave him access to Plantation House, seat of the Governor of St. Helena, Napoleon’s “gaoler” Sir Hudson Lowe.

Despite the restrictions that surrounded Longwood House, Napoleon's residence, O'Meara decided to conduct a clandestine correspondence with John Finlaison, a friend at the Admiralty in London. His letters recorded his private conversations with the illustrious captive, who became increasingly irritated by Sir Hudson Lowe.

In the autumn of 1817, when Napoleon's health began to decline, the Governor would not believe his physician's diagnosis. Pressure was exerted upon O'Meara, but to no avail, and finally, in July 1818, he was expelled from Longwood. Without medical assistance for over a year, and increasingly isolated in his wretched, damp abode, Napoleon’s health gradually deteriorated leading to his death in May 1821.

These clandestine letters offer an invaluable insight into Napoleon's state of mind during his captivity. O'Meara would later use them to compile his famous book, A Voice from St. Helena, in 1822. However, in the published work, he exercised restraint and softened the tone of the original letters which now for the first time are published in their entirety in Inside Longwood.