He was the eighth son of Edward Venables-Vernon-Harcourt, Archbishop of York, and began life as Octavius Henry Cyril Vernon at Rose Castle, Cumberland.
[1] Harcourt entered the Royal Navy in August 1806 as a midshipman on board the 74-gun Tigre, under the command of Captain Benjamin Hallowell, and in 1807 took part in the expedition to Egypt, witnessing the surrender of Alexandria, and was employed on boat-service on the Nile.
During the blockade of Toulon, he took part the action of October 1809 which led to the destruction of the French ships Robuste and Lion.
While off the coast of Italy, he landed with a party of seamen and marines near Piombino, captured a martello tower and brought out or destroyed a convoy which was anchored under its protection.
[2] During the Hundred Days, Harcourt served aboard the frigate Amelia, under Captain the Honourable Granville Proby, in the blockade of Elba, and when the news of the defeat of Napoleon at Waterloo arrived, was sent with a Major of the Tuscan army to summon the town of Porto Ferrajo to hear the announcement.