The attempt to rescue Napoleon with a submarine: fact or fiction?
Napoleonica. La Revue2011/2 (N° 11), pages 11 - 31
In his best selling biography of Napoleon published in 1827, Sir Walter Scott asserted that at some point in 1820 a certain Captain Thomas Johnstone, “a smuggler of an uncommonly resolute character”, had attempted to rescue Napoleon from St. Helena with a submarine. Many historians have dismissed this story as too farfetched. The article here, the most complete on this subject to date, brings to light some previously unrecognised contemporary accounts that, although sometimes conflicting and/or questionable in their details, lend credence to Scott’s assertion that some of Napoleon’s supporters seriously entertained the idea of rescuing him with a submarine and spent a considerable amount of money to build it. It also seems that the British government took this and other rescue plots seriously enough to derail them and to increase vigilance at St. Helena.
https://www.cairn.info/revue-napoleonica-la-revue-2011-2-page-11.htm