1739-1814. He was born in Dundee, Scotland on 24 January 1739, the son of the town clerk, Alexander Duncan, and of his wife, Isobel Crawford.
Having seen early employment in the merchant service, Duncan entered the navy in May 1755 as an able seaman aboard the Nassau 70, Captain George Cockburne, and was rated midshipman in the following year. He continued in that vessel under the command of Captain James Sayer, seeing service in the Mediterranean in 1756, and in the following year in North American waters where she participated in the unsuccessful attempt to capture Louisbourg.
After a year from February 1758 aboard the Newark 80, Captain William Holburne, he briefly joined the America 60, Captain Hon. John Byron, going out to the Mediterranean where he was immediately moved to the flagship of Vice-Admiral Thomas Broderick, the Prince 90, Captain Joseph Peyton, serving as a midshipman for four months, with his ship being present but unengaged at the Battle of Lagos Bay on 17-19 August 1759. Following the battle he was briefly aboard the Namur 90, Captain Matthew Buckle, the flagship of Admiral Hon Edward Boscawen, before that vessel returned home.
Duncan was commissioned lieutenant of the ancient guardship Barfleur 80, Captain John Fortescue, on 21 September 1759, moving at the end of the following year to the Hampton Court 64, Captain Carr Scrope. With this vessel he enjoyed a more active period, serving at the reduction of Belleisle in 1761 and at the capture of Havana in 1762, where the ship was commanded by Captain Alexander Innes. In October 1762 he joined the Téméraire 74, Captain Richard Bickerton, remaining at Jamaica before going on half-pay at the end of the war in the following year.
Duncan was promoted commander of the bomb Terror 8 on 26 May 1768, and from August 1769 commanded the brig Wasp 8 in home waters. He delivered pressed men from Ireland to Plymouth in October 1770 during the dispute over the Falkland Islands with Spain, but an attempt to board and press men from the East Indiaman Glatton at Gravesend during the Christmas period was met with an armed show of defiance. After leaving the Wasp in October 1772 he once more went on half-pay.
On 7 February 1776 he was posted captain of the newly commissioned Eagle 64, going out to North America three months later with the flag of Vice-Admiral Lord Howe, the new commander-in-chief. He was aboard this vessel during the New York campaign of July-October, and in the attack by the submersible Turtle on 6 September. Having assumed the duties of captain of the fleet whilst Roger Curtis became captain of the Eagle, Duncan led the naval force in operations against the Connecticut town of Danbury in April 1777. He was present in the Philadelphia campaign of August-November where he superintended the flat-boat landings in the Elk River, and he served at the defence of New York in July 1778 and operations off Rhode Island in August. Shortly afterwards the Eagle returned to England upon Lord Howe resigning his command of the North American station. and Duncan went on half-pay. During October he was sent by the first lord of the Admiralty, the Earl of Sandwich, to visit the King at Windsor so that he could answer any questions pertaining to the recent course of events in North America.
In September 1780 he was appointed to the Medea 28, going out to North America from Portsmouth in early October with instructions for General Sir Henry Clinton. In January 1781 he arrived off Charleston from a cruise having captured the Philadelphia-based Morning Star 18 on 14 January. He fought at the Battle of Cape Henry on 16 March, following which he was despatched to reconnoitre the Delaware. A further capture was the Massachusetts frigate Protector 26 on 5 May when he was returning with the Roebuck 44, Captain Sir Andrew Snape Hamond, from a reconnaissance of Rhode Island. After briefly visiting Halifax he took the privateer Phoenix on 1 June, the Rover 18 off Salem on 20 June, the sloop Revenge 10, the swift Salem-based Belisarius 20 on 7 August off the Delaware, the Marianne 12 on 13 August, and the Favourite 14 on 29 August. The Medea was then present at the Battle of the Chesapeake on 5 September before departing North America with Rear-Admiral Thomas Graves’ dispatches.
On 9 October, whilst off the west coast of Ireland on her passage home, the Medea engaged in a five-hour chase of the Black Princess 26, a letter-of-marque that had allegedly been issued by the King of France, but was commanded by a British subject from Ireland, Edward M’Carty. Duncan laid a gun which carried away the other vessel’s maintop-mast, allowing the Medea to close within hail and confirm her surrender. Upon M’Carty and several other Britons being discovered they were brought to trial on the following 30 March, and despite M’Carty’s defence that he had struck his colours and ceased to resist as soon as the smaller Medea had hailed him, he was found guilty of piracy and sentenced to death.
In the meantime Duncan had arrived at the Admiralty with Graves’ dispatches on the evening of 13 October 1781 after putting into Weymouth. From November he commanded the Ambuscade 32, serving out of Plymouth and being sent to search for a privateer off the Lizard in January 1782. On 19 April he joined the Victory 100, the flagship of Admiral Lord Richard Howe in the Channel, being present in the summer campaign of April-August, and at the relief of Gibraltar on 18 October. On 7 November he arrived at the Admiralty once more, having been given the honour of taking home Howe’s dispatches, and thereafter he saw no further service in the American Revolutionary War.
In August 1783 he sailed for Nova Scotia to become the commissioner at Halifax dockyard, having been appointed to that office by his friend Howe, now the first lord of the Admiralty. He came home in 1799 to seek medical treatment, assumed a similar position at Sheerness at the end of April 1800, and on 1 January 1801 became deputy comptroller of the Navy, a position he relinquished on 7 June 1806 when he retired to Dartmouth.
Captain Duncan died in Dartmouth on 7 October 1814.
He married Mary French at St. Saviour’s Church, Dartmouth, on 27 November 1761. A son, Henry Duncan, entered the Navy in 1781 but was lost off the coast of Newfoundland in the Scout 18 in November 1802. Additionally he had a daughter, Isabella and another son, Arthur French Duncan.
King George III described Duncan as a ‘sensible though very cautious man’.