Question: When did the era when Richard Cosway was a leading English portrait painter end?

Context paragraphs:
Tilly Kettle: Tilly Kettle (1735–1786) was a portrait painter and the first prominent English portrait painter to operate in India.

Thomas Lawrence: Sir Thomas Lawrence PRA FRS (13 April 1769 – 7 January 1830) was a leading English portrait painter and the fourth president of the Royal Academy.

John Smart: John Smart (c. 1740–1811), was an English painter of portrait miniatures.  He was a contemporary of Richard Cosway, George Engleheart, William Wood and Richard Crosse.

Regency era: The Regency in Great Britain was a period when King George III was deemed unfit to rule and his son ruled as his proxy as Prince Regent.  On the death of George III in 1820, the Prince Regent became George IV.  The term Regency (or Regency era) can refer to various stretches of time; some are longer than the decade of the formal Regency which lasted from 1811–1820.  The period from 1795 to 1837, which includes the latter part of the reign of George III and the reigns of his sons George IV and William IV, is often regarded as the Regency era, characterised by distinctive trends in British architecture, literature, fashions, politics, and culture.  The Regency era ended in 1837 when Queen Victoria succeeded William IV.

Richard Crosse: Richard Crosse (1742–1810) was a leading English painter of portrait miniatures.  He was a contemporary of John Smart, George Engleheart, Richard Cosway and William Wood.

Mary Beale: Mary Beale ("née" Cradock; 26 March 1633 – 1699) was one of the most successful professional female Baroque era portrait painters of the late 17th century due to her perseverance of her business.  Praised by Richard Gibson and court painter Peter Lely, she is considered as successful as Joan Carlile.  Joan Carlile was also an English portrait painter who was one of the first women to practice painting professionally Mary Beale managed to be the financial provider for her family through her professional portrait business.  Her book "Observations", although it was never officially published, was one of the first instructional books ever written by a woman and boldly announced her authority on painting.  Mary Beale stood apart from other women due to her outspokenness and successful business that allowed her to be the breadwinner of the family.

William Bell (artist): William Bell, born about 1734/5, was an English portrait painter originally from Newcastle upon Tyne.  In around 1768 he moved to London, to be a student in the Royal Academy of Arts.  While there, in the year of 1771, he received a gold medal for his painting of Venus entreating Vulcan to forge arms for her son Æneas.  William Bell's best known works were the portraits painted for the family of Delaval, of Seaton Delaval Hall.  These paintings earned Bell the patronage of Lord Delaval, and in 1775 he exhibited two views of Delaval Hall.  A portrait he painted of Robert Harrison, 1715-1802, is displayed in the National Portrait Gallery, London.  William Bell died on 8 June 1794 and was buried 10 June, St Andrew's Church, Newcastle upon Tyne; his death was reported in the Newcastle Courant (14 June 1794) thus: "DIED, Sunday morning, Mr William Bell, an eminent Portrait Painter, whose memory will be esteemed at long as his animated productions remain, many of which bear testimony to his abilities in this part of the kingdom".

Richard Cosway: Richard Cosway {'1': ", '2': ", '3': 'RA', '4': "} (5 November 1742 – 4 July 1821) was a leading English portrait painter of the Regency era, noted for his miniatures.  He was a contemporary of John Smart, George Engleheart, William Wood, and Richard Crosse.  His wife was the Italian-born painter Maria Cosway, a close friend of Thomas Jefferson.

Pompeo Batoni: Pompeo Girolamo Batoni (25 January 1708 – 4 February 1787) was an Italian painter who displayed a solid technical knowledge in his portrait work and in his numerous allegorical and mythological pictures.  The high number of foreign visitors travelling throughout Italy and reaching Rome during their Grand Tour, made the artist specialized in portraits.  Batoni won international fame largely thanks to his customers, mostly British of noble origin, whom he portrayed, often with famous Italian landscapes in the background.  Such "Grand Tour" portraits by Batoni were in British private collections, thus ensuring the genre's popularity in the United Kingdom.  One generation later, Sir Joshua Reynolds would take up this tradition and become the leading English portrait painter.  Although Batoni was considered the best Italian painter of his time, contemporary chronicles mention of his rivalry with Anton Raphael Mengs.

Francis Parsons (painter): Francis Parsons (fl.  1763–1783, died 1804) was an English portrait painter.  He was a student at the drawing academy in St. Martin's Lane.  In 1763 he exhibited at the Society of Artists' exhibition in Spring Gardens portraits of an Indian chief and of Miss Davies the actress.  Parsons was a member of the Incorporated Society of Artists, and served as director in 1775 and the following years, and as their treasurer in 1776.  A portrait of James Brindley the engineer, by Parsons, was engraved in mezzotint by R. Dunkarton in 1770, and published by Parsons at his house in Great Ormond Street, London.  The same portrait was also engraved by Cook.  Another portrait of Cunne Shote, a Cherokee chief, by Parsons, was engraved in mezzotint by J. McArdell.  As he did not succeed greatly in portraiture, Parsons latterly kept a shop as a dealer in and restorer of pictures.  He exhibited for the last time in 1783.

Supporting paragraphs: Richard Cosway Regency era
Answer: 1837