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His Grace The Duke of Devonshire KG
Portrait of the Duke of Devonshire painted in Rome byPompeo Batoni, 1768
Lord High Treasurer of Ireland
In office 13 March 1766 – 1793
Monarch	George III
Preceded by	Vacant William Cavendish, 4th Duke of Devonshire, 1764
Succeeded by	In Commission Richard Boyle, 2nd Earl of Shannon, First Lord
Personal details
Born	(1748-12-14)14 December 1748
Died	29 July 1811(1811-07-29) (aged 62)
Spouses	Lady Georgiana Spencer ​ ​ (m. 1774; died 1806)​ Lady Elizabeth Hervey ​ ​ (m. 1809)​
Children	Charlotte Williams (illegitimate) Georgiana Howard, Countess of Carlisle Harriet Leveson-Gower, Countess Granville William Cavendish, 6th Duke of Devonshire Caroline St. Jules (illegitimate) Sir Augustus Clifford, 1st Baronet (illegitimate)
Parents	William Cavendish, 4th Duke of Devonshire Charlotte Boyle, 6th Baroness Clifford

William Cavendish, 5th Duke of Devonshire,KG (14 December 1748 – 29 July 1811), was a British nobleman, aristocrat, and politician. He was the eldest son ofWilliam Cavendish, 4th Duke of Devonshire, by his wife, the heiressLady Charlotte Boyle,suo jure Baroness Clifford, who brought in considerable money and estates to the Cavendish family. He was invited to join the Cabinet on three occasions, but declined each offer.^[1] He wasLord High Treasurer of Ireland and Governor of Cork, and Lord Lieutenant of Derbyshire.^[1] In 1782, he was made a Knight of theOrder of the Garter.

The 5th Duke is most widely known for his marriage to his first wifeGeorgiana, Duchess of Devonshire. At the age of about twenty-one, Devonshire toured Italy withWilliam Fitzherbert which is where they commissioned the pair of portraits byPompeo Batoni.^[2]

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He was married twice: first, toLady Georgiana Spencer (1757–1806), daughter ofJohn Spencer, 1st Earl Spencer; second, toLady Elizabeth Foster, née Hervey (1759–1824),^[3] daughter of the4th Earl of Bristol; Lady Elizabeth had been his mistress and his first wife's friend and confidante for more than twenty years.

By his first wife, he had one son named (William Cavendish, 6th Duke of Devonshire, sometimes called "The Bachelor Duke", who succeeded him and who died unmarried in 1858), and two daughters:Lady Georgiana "Little G" Cavendish, later the Countess of Carlisle (wife ofGeorge Howard, 6th Earl of Carlisle), andLady Harriet "Harryo" Cavendish, later the Countess Granville (wife ofLord Granville Leveson-Gower, who would be created 1stEarl Granville).^[3]

Both daughters left descendants and the title ofClifford barony fell intoabeyance between them. The dukedom and estates would pass to a grandson of a younger brother of the 5th Duke of Devonshire; however, the7th Duke of Devonshire would marry a daughter of the6th Earl of Carlisle, who was thus a granddaughter of the 5th Duke and niece of the 6th Duke.^[3]

Georgiana Cavendish eventually became a socialite who had gathered around her a large circle of literary, political friends.Thomas Gainsborough andJoshua Reynolds painted her; the Gainsborough painting would be later disposed of by the 5th Duke and was recovered much later, after many vicissitudes.

By his second wife,Lady Elizabeth Foster, he had no legitimate issue, but the couple had two illegitimate children born before their marriage. A son, Augustus, was given the surname Clifford and becameSir Augustus Clifford and rose to be an admiral in theRoyal Navy and theGentleman Usher of the Black Rod in theHouse of Lords; his descendants would die out in the male line in 1895. The Duke's daughter by Lady Elizabeth, Caroline, was given a different surname from her brother, St. Jules. Caroline St. Jules would marry theHon. George Lamb, a brother of the2nd Viscount Melbourne (himself married toLady Caroline Ponsonby, niece ofLady Georgiana Spencer, the 5th Duke's 1st wife). Caroline and George Lamb had no issue.

The 5th Duke had a daughter—Charlotte, given the surname Williams—by his mistress, Charlotte Spencer, the daughter of an indigent clergyman. His first child was born shortly following his marriage to Lady Georgiana Spencer (no relation to his mistress). Charlotte would later marry suitably.

When themilitia was called out during theWar of American Independence the duke was appointedcolonel of theDerbyshire Militia by his uncle,Lord George Cavendish,Lord Lieutenant of Derbyshire. Taking command in April 1778, he immediately had to deal with a mutiny by his men over pay, and then march them toCoxheath Camp inKent, where a large encampment had been formed.^[4] Here Duchess Georgiana was prominent among the fashionable army wives and appeared in caricatures as 'Lady Gorget', the real colonel in full uniform, interviewing recruits for the regiment.^[5] The war ended with thePeace of Paris and the militia were disembodied in March 1783. Having recently taken over as Lord Lieutenant of Derbyshire himself, the Duke resigned the command in October and appointed his younger brotherLord George Henry Cavendish as colonel in his place.^[4]

The fifth Duke would be closely involved with the nearbyspa town ofBuxton. He used the profits from hiscopper mines to transform the town into a replica ofBath, including theCrescent Hotel and an octagonal set ofstables, which later became theDevonshire Dome.

• 
  Statue of William Cavendish, 5th Duke of Devonshire inBuxton
• 
  Coat of arms of William Cavendish, 5th Duke of Devonshire, KG

• In the filmThe Duchess, about Georgiana, the fifth Duke is played byRalph Fiennes.

• Hansard 1803–2005:contributions in Parliament by the Duke of Devonshire

• 1748 births
• 1811 deaths
• Cavendish family
• Dukes of Devonshire
• Barons Clifford
• Children of William Cavendish, 4th Duke of Devonshire
• Knights of the Garter
• Lord-lieutenants of Derbyshire
• Derbyshire Militia officers
• Lord high treasurers of Ireland

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