Question: In which year did this British peer and politician whose daughter was Henrietta Ponsonby, Countess of Bessborough pass away?

Context articles: Frederick Cavendish Ponsonby
Walter Ponsonby, 7th Earl of Bessborough
Brabazon Ponsonby, 1st Earl of Bessborough
Henrietta Ponsonby, Countess of Bessborough
John Spencer, 1st Earl Spencer
Earl of Bessborough
Baron de Mauley
Baron Ponsonby of Imokilly
Ponsonby baronets
Baron Ponsonby of Shulbrede

Major General Sir Frederick Cavendish Ponsonby (6 July 1783 – 11 January 1837), styled The Honourable Frederick Cavendish Ponsonby from 1806 to 1837, was a British military officer, the second son of the 3rd Earl of Bessborough and Henrietta Ponsonby, Countess of Bessborough.
Walter William Brabazon Ponsonby, 7th Earl of Bessborough (13 August 1821 – 24 February 1906), was a British peer and member of the House of Lords.
 He was the fifth son of John Ponsonby, 4th Earl of Bessborough, and his wife Lady Maria Fane.
 He inherited the earldom on 11 March 1895 when his elder brother Frederick Ponsonby, 6th Earl of Bessborough, died unmarried and without a male heir.
Brabazon Ponsonby, 1st Earl of Bessborough (1679 – 4 July 1758) was a British politician and peer.
 He was the son of William Ponsonby, 1st Viscount Duncannon and Mary Moore.
 He was an active politician from 1705 to 1757 in Great Britain and Ireland.
 He represented Newtownards and County Kildare in the Irish House of Commons.
 He inherited his father's viscountcy in 1724 and was made Earl of Bessborough in the Peerage of Ireland in 1739.
 He is buried in Fiddown, County Kilkenny, Ireland.
Henrietta Ponsonby, Countess of Bessborough (16 June 1761 – 11 November 1821), born Lady Henrietta Frances Spencer (generally called Harriet), was the wife of Frederick Ponsonby, 3rd Earl of Bessborough, and mother of the notorious Lady Caroline Lamb.
 Her father, John Spencer, 1st Earl Spencer, was a great-grandson of John Churchill, 1st Duke of Marlborough.
 Her sister was Georgiana Cavendish, Duchess of Devonshire.
John Spencer, 1st Earl Spencer (19 December 1734 – 31 October 1783) was a British peer and politician.
Earl of Bessborough is a title in the Peerage of Ireland.
 It was created in 1739 for Brabazon Ponsonby, 2nd Viscount Duncannon, who had previously represented Newtownards and County Kildare in the Irish House of Commons.
 In 1749 he was given the additional title of Baron Ponsonby of Sysonby, in the County of Leicester, in the Peerage of Great Britain, which entitled him to a seat in the British House of Lords.
 The titles Viscount Duncannon, of the fort of Duncannon in the County of Wexford, and Baron Bessborough, of Bessborough, Piltown, in the County of Kilkenny, had been created in the Peerage of Ireland in 1723 and 1721 respectively for Lord Bessborough's father William Ponsonby, who had earlier represented County Kilkenny in the Irish House of Commons.
Baron de Mauley, of Canford in the County of Dorset, is a title in the Peerage of the United Kingdom.
 It was created in 1838 for the Whig politician the Hon. William Ponsonby, who had earlier represented Poole, Knaresborough and Dorset in the House of Commons.
 He was the third son of the 3rd Earl of Bessborough, an Anglo-Irish peer, and the husband of Lady Barbara Ashley-Cooper, one of the co-heirs to the ancient barony by writ of Mauley (or Maulay), which superseded the feudal barony the "caput" of which was at Mulgrave Castle, Yorkshire, which barony by writ had become extinct in 1415.
 His son, later the second Baron, sat as Member of Parliament for Poole and Dungarvon.
 s of 2009 the title is held by the latter's great-great-grandson, the seventh Baron, who succeeded his uncle in 2002.
 He is one of the ninety elected hereditary peers that remain in the House of Lords after the passing of the House of Lords Act 1999, and sits as a Conservative.
 He was elected in 2005 and thereby became the first hereditary peer having succeeded to his title after the House of Lords Act of 1999, to have obtained an elective hereditary peers seat in the House of Lords.
 As a descendant of the third Earl of Bessborough, Lord de Mauley is also in remainder to the earldom of Bessborough and its subsidiary titles.
Baron Ponsonby, of Imokilly in County Cork, also referred to as Baron Ponsonby of Imokilly, in the County of Cork, was a title in the Peerage of the United Kingdom.
 It was created in 1806 for the William Ponsonby, who had previously represented Cork City, Bandonbridge and Kilkenny in the Irish House of Commons and Kilkenny in the British House of Commons.
 A member of the influential Ponsonby family, he was the eldest son of the Honourable John Ponsonby, second son of Brabazon Ponsonby, 1st Earl of Bessborough (see Earl of Bessborough for earlier history of the family).
 His son, the second Baron, was a prominent diplomat and notably served as Ambassador to the Ottoman Empire and Austria.
 In 1839 he was created Viscount Ponsonby, of Imokilly in the County of Cork, in the Peerage of the United Kingdom.
 He was childless and the viscountcy became extinct on his death in 1855.
 He was succeeded in the barony by his nephew, the third Baron.
 He was the posthumous son of the Honourable Sir William Ponsonby, second son of the first Baron.
 Lord Ponsonby died childless and was succeeded by his first cousin, the fourth Baron.
 He was the son of the Right reverend the Honourable Richard Ponsonby, third son of the first Baron.
 He died unmarried in 1866 when the barony became extinct.
The Ponsonby Baronetcy, of Wootton in the County of Oxford, is a title in the Baronetage of the United Kingdom.
 It was created on 27 January 1956 for the Conservative politician Charles Ponsonby.
 He had earlier represented Sevenoaks in the House of Commons and served as Parliamentary Private Secretary to the Foreign Secretary Anthony Eden from 1941 to 1945.
 A member of the prominent Ponsonby family headed by the Earl of Bessborough, he was the son of the Hon. Edwin Charles William Ponsonby, fourth son of Charles Ponsonby, 2nd Baron de Mauley.
 As of 2010 the title is held by the second Baronet's son, the third Baronet, who succeeded in 2010.
 His father was Lord Lieutenant of Oxfordshire between 1980 and 1996.
 As a descendant of the second Baron de Mauley, he is also in remainder to this title as well as to the earldom of Bessborough.
Baron Ponsonby of Shulbrede, of Shulbrede in the County of Sussex, is a title in the Peerage of the United Kingdom.
 It was created in 1930 for the politician Arthur Ponsonby.
 Ponsonby was the third son of General Sir Henry Ponsonby and the great-grandson of Frederick Ponsonby, 3rd Earl of Bessborough.
 Frederick Ponsonby, 1st Baron Sysonby, was his elder brother.
 The first Baron's grandson, the third Baron, was also a Labour politician and notably served as Opposition Chief Whip in the House of Lords in the 1980s.
 s of 2010 the title is held by the latter's only son, the fourth Baron, who succeeded in 1990.
 He sat on the Labour benches in the House of Lords prior to the passing of the House of Lords Act 1999, when he lost his seat.
 However, in 2000 he was given a life peerage as Baron Ponsonby of Roehampton, of Shulbrede in the County of West Sussex, and was able to retake his seat in the House of Lords.
 As a descendant of the third Earl of Bessborough, he is also in remainder to this peerage and its subsidiary titles.