He sailed with George Vancouver on his voyages of exploration, captained Bordelais, Africaine and Thalia, and was the chief suspect in the "delicate investigation" into the morals of Caroline, Princess of Wales.
The Admiralty had ordered Vancouver to complete a survey of the north-west coast of North America and take possession of disputed land at Nootka Sound on the island that is now named after him.
The two ships called at New Zealand, Tahiti and Hawaii before reaching the starting point for the American survey, the Strait of Juan de Fuca, almost exactly a year after setting out.
Manby recorded first impressions of the coast: "It had more the aspect of enchantment than reality, with silent admiration each discerned the beauties of Nature, and nought was heard on board but expressions of delight murmured from every tongue.
Imperceptibly our Bark skimmed over the glassy surface of the deep, about three Miles an hour, a gentle breeze swelled the lofty Canvass whilst all was calm below".
They arrived at Nootka Sound in the autumn of 1792 and, when disputes arose with the Spanish, several officers were sent back to England to request instructions from the Admiralty.
Manby wrote that Vancouver: "is grown Haughty Proud Mean and Insolent, which has kept himself and his Officers in a continual state of wrangling..."[2] The expedition returned in 1795, by which time England was at war with France.
Manby spent the next year as a lieutenant in the 84-gun Juste and then in early 1797 was appointed as commander of the 44-gun HMS Charon, guarding trade in Irish Sea and the Channel.
[3] Back in Plymouth, George Manby underwent an operation to remove slugs and rotting hat from his skull (he had been shot by his wife's lover some years previously).
After the Treaty of Amiens temporarily brought a halt to hostilities between Britain and France, Manby was appointed to the Juno and returned to England, where the ship was paid off.
In October 1802 the Earl of St Vincent, first Lord of the Admiralty, sent for him and said 'I don't like to see an active officer idle on shore; I therefore give you the Africaine, one of the finest frigates in the British navy'.
While HMS Africaine was fitting out at Deptford Dockyard, Manby was a frequent visitor to Montagu House in Blackheath where the princess, who was estranged from her husband the prince of Wales, lived.
She bought the soft furnishings for his cabin and asked the Admiralty to send the Africaine to attend her in the Downs when she rented a house at Ramsgate in the summer.
By the time the Africaine reached England she had lost nearly one-third of her crew and officers, and had to spend forty days in quarantine off the Isles of Scilly.
If jugs of water and towels were left in the passage when Manby visited it was proof, Perceval argued, of the servants' slovenliness and not of high treason.