1718-82. He was born in October 1718 at Westminster, the son of Swedish-born Magnus Kempenfelt, who was a lieutenant-colonel in the army and governor of Jersey in the 1720?s, and of his wife, Anne Hunt. He was the brother of Gustavus Kempenfelt, an army captain.
After entering the navy at the age of ten Kempenfelt saw his first service at the siege of Porto Bello under Vice-Admiral Edward Vernon in 1739. On 14 January 1741 he was promoted lieutenant of this officer’s flagship, the Strafford 60, Captain Thomas Trevor, and he afterwards served in the Superbe 60 and the frigate Seahorse 20 before returning to England at the end of 1746.
In September 1748 he was appointed to the Anson 60, Captain Hon. Augustus Keppel, and from January 1755 served successively aboard the Lichfield 50, and from April the Orford 66, both vessels commanded by Captain Charles Steevens.
Kempenfelt was appointed to the command of the fireship Lightning on 5 May 1756, and on 17 January 1757 was posted to the Elizabeth 70 as flag captain to Commodore Charles Steevens under orders for the East Indies. He fought in Vice-Admiral George Pocock?s actions with the French off Cuddalore on 29 April 1758, and off Negapatam on 3 August 1758, and later in the same year removed to the frigate Queenborough 20. On 16 February 1759 he led a small squadron consisting of another 20-gun ship and six other vessels that raised the French siege of Madras. Once more he became flag captain to the promoted Rear-Admiral Charles Stevens after joining the Grafton 70 in the early summer of 1759, fighting at the Battle of Pondicherry on 10 September, and then transferring in the summer of 1760 to the Norfolk 74.
In 1761, Rear-Admiral Steevens having passed away, he distinguished himself as flag captain to Rear-Admiral Sam Cornish at the capture of Manila, and he was appointed governor of Cavite in the Philippines by General William Draper for a short while before returning to England with Cornish?s despatches. Without being offered any reward he was then sent back to the East Indies to resume his former position aboard the Norfolk, and he returned to England at the peace of 1763.
Apart from a brief spell in command of the Buckingham 70 during the Spanish dispute at the end of 1770 he was not re-employed until 1778. During the years of peace he travelled to the continent and made a study of shipbuilding techniques, whilst also examining French harbours and coastal waters.
In October 1778 he was appointed to the brand new Alexander 74, and in April of the following year sat on the court martial of Vice-Admiral Sir Hugh Palliser in the wake of the Battle of Ushant which had taken place on 27 July 1778. On 24 March 1779 he became captain of the fleet to Admiral Sir Charles Hardy in the Channel on the King?s insistence, serving on the Victory 100, Captain Henry Collins. He had earlier been nominated for the post by Captain John Elliot who had been chosen in the first instance but believed Kempenfelt to be the most proficient officer in the service. This was a rather invidious position for Kempenfelt who was not alone in regarding the aged Hardy as the wrong choice for commander-in-chief. It must therefore have been with some reservations as to his commander?s ability that he took part in the Channel Fleet retreat of August 1779.
After Hardy stepped down Kempenfelt was captain of the fleet in 1780 to Admiral Francis Geary aboard the Victory 100, Captain Samuel Wittewronge Clayton. On 26 September 1780 he was promoted rear-admiral, and he was present in the Channel fleet campaign of June-December 1780. Later in 1780 he became captain of the fleet to the new commander-in-chief, Vice-Admiral George Darby, serving aboard the Britannia 100, Captain James Bradby at the relief of Gibraltar on 12 April 1781, and he was then third-in-command in the campaign from June- November.
On 10 September 1781 he hoisted his flag aboard the Victory 100, Captain Henry Cromwell, and on 12 December achieved a brilliant tactical victory off Ushant when his inferior force of twelve ships took nine prizes out of a French East India convoy escorted by De Guichen’s larger fleet of nineteen ships. He also sunk four frigates and captured a number of pther merchantmen.
In March 1782 he transferred his flag to the Royal George 100, Captain Henry Cromwell and from May 1782 Captain Martin Waghorn, forming part of Admiral Lord Howe’s Channel fleet from April. On 20 April, whilst on detached duty under the orders of Vice-Admiral Hon. Samuel Barrington, he rescued the Buffalo 60, Captain George Robertson, from three French sail of the line in the same engagement that saw Captain John Jervis of the Foudroyant bring the P?gase to action and capture her. During May he was based off Brest whilst another division of the fleet was off the Texel.
At Spithead on 29 August the Royal George was given a ?parliament heel? to correct underwater defects, but upon being over-heeled the water rushed into her lower gun-ports which had been left open to take in stores and she quickly sank. Kempenfelt was in his cabin at the time of the tragedy and was one of the eight hundred men women and children who drowned.
A bachelor, Kempenfelt was noted for the care of his men, for the divisional system to enhance officer responsibility, and for the introduction of French tactics and ideas. He was known as the ?brains of the navy? and Admirals Howe, Nelson, Jervis and Duncan later adapted his principles and tactics in later battles to earn themselves famous victories. Together with Howe he drafted the ?Steadfast Fighting Laws?, and he improved Howe’s innovative signalling system, basing it on nine flags which allowed up to ninety-nine different signals to be generated. Even so, many officers could not understand the codes, a fact which greatly upset him, as did the fact that they did not take to his melee tactics. He worked hard on managing Admirals Hardy and Geary in his position of captain of the fleet, but felt constrained to criticise both officers.
Practical and evangelical, he wrote religious verse, was pious and benevolent, modest, plain and honest, brave, experienced, judicious, cool, sedate and temperate. Such was his popularity that fifteen years after his death the mutineers at Spithead distributed pamphlets requesting peace ?in the spirit of Kempenfelt?. Affectionately known as ?Kempy?, he was tall and stooped in appearance. He was a good friend of the equally proficient and evangelical Admiral Lord Barham.