Question: When did Henrietta Ponsonby's father die?

Passages:
Lady Caroline Lamb (née Ponsonby; 13 November 1785 – 25 January 1828), known as the Honourable Caroline Ponsonby until her father succeeded to the earldom in 1793, was an Anglo-Irish aristocrat and novelist, best known for her affair with Lord Byron in 1812.  Her husband was The Hon. William Lamb, who later became Viscount Melbourne and Prime Minister.  However, she was never the "Viscountess Melbourne" because she died before Melbourne succeeded to the peerage; hence, she is known to history as "Lady" Caroline Lamb. 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. 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. 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. Henry Dermot Ponsonby Moore, 12th Earl of Drogheda (born 1937) is a British photographer known professionally as Derry Moore.  He inherited the title of Earl of Drogheda from his father, Charles Moore, 11th Earl of Drogheda (1910-1989).  His mother was the late Joan Eleanor Carr (died 1989). 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. Dr James Alfred Ernest Corea was a Sri Lankan public official.  He was born in 1870.  His father was Charles Edward Bandaranaike Corea who was a Proctor of the Supreme Court.  His mother was Henrietta Seneviratne.  J.A.E Corea's father died in 1872 when his youngest son Victor was just one.  His wife Henrietta was a widow from the age of 21. John Spencer, 1st Earl Spencer (19 December 1734 – 31 October 1783) was a British peer and politician. Lord Dingwall is a title in the Peerage of Scotland.  It was created in 1609 for Sir Richard Preston, with remainder to his heirs whatsoever.  In 1619 he was further honoured when he was made Baron Dunmore and Earl of Desmond in the Peerage of Ireland, with remainder to heirs male.  On his death in 1628 the Irish titles became extinct while he was succeeded in the Scottish lordship by his daughter Elizabeth, the second Lady Dingwall.  She was the wife of James Butler, 1st Duke of Ormonde.  Their eldest son Thomas Butler, Earl of Ossory, was summoned by writ to the English Parliament as Baron Butler, of Moore Park, in 1666.  However, he predeceased his parents who were both succeeded by their grandson, the second Duke and third Lord Dingwall.  He had already succeeded his father as second Baron Butler.  However, the Duke was attainted in 1715 and his titles forfeited.  In 1871, Francis Cowper, 7th Earl Cowper, managed to obtain a reversal of the attainder of the lordship of Dingwall and barony of Butler and became the fourth Lord Dingwall and third Baron Butler.  He was the great-great-great-grandson of Henrietta Butler, Countess of Grantham (wife of Henry de Nassau d'Auverquerque, 1st Earl of Grantham), second daughter of Thomas Butler, Earl of Ossory and 1st Baron Butler, whose second daughter Lady Henrietta de Nassau d'Auverquerque married William Clavering-Cowper, 2nd Earl Cowper.  In 1880 he also succeeded his mother as eighth Baron Lucas of Crudwell.  For later history of the lordship of Dingwall and barony of Butler, see the Baron Lucas of Crudwell.

Supporting sentences:
 Her father, John Spencer, 1st Earl Spencer, was a great-grandson of John Churchill, 1st Duke of Marlborough. John Spencer, 1st Earl Spencer (19 December 1734 – 31 October 1783) was a British peer and politician.