In what year were the parents of Prince Octavius of Great Britain married?  
1761
Charlotte of Mecklenburg-Strelitz
Charlotte of Mecklenburg-Strelitz (Sophia Charlotte; 19 May 1744 – 17 November 1818) was by marriage to King George III the Queen of Great Britain and Ireland from her wedding in 1761 until the union of the two kingdoms in 1801, after which she was Queen of the United Kingdom of Great Britain and Ireland until her death in 1818.
 She was also the Electress of Hanover in the Holy Roman Empire until the promotion of her husband to King of Hanover on 12 October 1814, after which she was also queen consort of Hanover.
Prince Octavius of Great Britain
Prince Octavius (23 February 1779 – 3 May 1783) was the 13th child and 8th son of King George III and his queen consort Charlotte of Mecklenburg-Strelitz.
 Six months after the death of his brother Prince Alfred, Octavius was inoculated with the smallpox virus.
 Several days later, he became ill.
 His subsequent death at the age of four devastated his parents, and in particular his father.
 George bemoaned the death of his son, of whom he was exceedingly fond; the king's later bouts of madness would involve hallucinations of his young son.
Earl Coningsby
Earl Coningsby was a title in the Peerage of Great Britain.
 It was created in 1719 for Thomas Coningsby, 1st Baron Coningsby, with remainder to his eldest daughter (by his second wife Lady Frances Jones), Margaret Newton, 1st Viscountess Coningsby, and the heirs male of her body.
 He was the great-grandson of the soldier and politician Sir Thomas Coningsby.
 Coningsby had already been created Baron Coningsby, of Clanbrassil, in the Peerage of Ireland in 1693, with normal remainder to heirs male, and Baron Coningsby in the Peerage of Great Britain in 1716, with similar remainder as for the earldom.
 On Lord Coningsby's death in 1729 he was succeeded in the Irish barony of 1692 by his grandson Richard Coningsby, the second Baron, the son of one of Coningsby's sons from his first marriage to Barbara Georges.
 However, Richard died already the same year, when the barony became extinct.
 Lord Coningsby was succeeded in the English barony and the earldom according to the special remainder by his daughter Margaret Newton, 1st Viscountess Coningsby.
 She had already in 1716 been made Baroness Coningsby, of Hampton Court in the County of Hereford, and Viscountess Coningsby in her own right.
 Both titles were in the Peerage of Great Britain.
 Lady Coningsby was the wife of Sir Michael Newton, 4th Baronet, of Barrs Court (see Newton Baronets).
 She had no surviving male issue and the titles became extinct on her death in 1759. Duke of Rothesay
Duke of Rothesay (Scottish Gaelic: "Diùc Baile Bhòid" , Scots: "Duik o Rothesay" ) is a dynastic title of the heir apparent to the British throne, currently Prince Charles.
 It was a title of the heir apparent to the throne of the Kingdom of Scotland before 1707, of the Kingdom of Great Britain from 1707 to 1801, and now of the United Kingdom of Great Britain and Northern Ireland.
 It is the title mandated for use by the heir apparent when in Scotland, in preference to the titles "Duke of Cornwall" (which also belongs to the eldest living son of the monarch, when and only when he is also heir apparent, by right) and "Prince of Wales" (traditionally granted to the heir apparent), which are used in the rest of the United Kingdom and overseas.
 The Duke of Rothesay also holds other Scottish titles, including those of Earl of Carrick, Baron of Renfrew, Lord of the Isles and Prince and Great Steward of Scotland.
 The title is named after Rothesay on the Isle of Bute, Argyll and Bute, but is not associated with any legal entity or landed property, unlike the Duchy of Cornwall. Royal Photographic Society
The Royal Photographic Society of Great Britain, commonly known as the Royal Photographic Society (RPS), is one of the world's oldest photographic societies.
 It was founded in London, England in 1853 as The Photographic Society of London with the objective of promoting the art and science of photography, and in 1854 received Royal patronage from Queen Victoria and Prince Albert.
 A change to the society's name to reflect the Royal patronage was, however, not considered expedient at the time.
 In 1874 it was renamed the Photographic Society of Great Britain, and from 1894 it became known as The Royal Photographic Society of Great Britain.
 A registered charity since 1962, in July 2004, The Royal Photographic Society of Great Britain was granted a Royal charter recognising its eminence in the field of photography as a learned society.
 For most of its history the Society was based at various premises in London.
 It moved to Bath in 1979, and since 2004 its headquarters has been at Fenton House in Bath, England.
 Membership is international and open to anyone with an interest in photography. Augustus d'Este
Sir Augustus Frederick d'Este, (13 January 1794 – 28 December 1848) was the son of Prince Augustus Frederick, Duke of Sussex, and Lady Augusta Murray, and a grandson of King George III.
 His parents were secretly married on 4 April 1793, in a Church of England ceremony in the Hotel Sarmiento, Rome, and later married again on 5 December 1793 at St George's, Hanover Square, Westminster, using their correct names but without revealing their identities.
 Both marriages were in defiance of the Royal Marriages Act 1772 and were thus legally null and void, at least in English law.
 After the birth of their first child, the marriage was discovered by the King and formally annulled, making their son illegitimate in Great Britain. Prince Alfred of Great Britain
Prince Alfred (22 September 1780 – 20 August 1782) was a member of the British Royal Family as the 14th child and 9th son of King George III and his queen consort Charlotte of Mecklenburg-Strelitz.
 Alfred became ill after his inoculation against the smallpox virus; his early death at the age of nearly two, along with the demise of his brother Prince Octavius six months later, was a shock to their parents.
 In his later bouts of madness King George would have imagined conversations with both of his youngest sons. Attulus saltator
Attulus saltator (formerly Sitticus saltator) is a species of jumping spider, from the Sitticinae subfamily.
 It was first described by Frederick Octavius Pickard-Cambridge in 1868 and has a Palearctic distribution, including Great Britain. Polignac Memorandum
The Polignac Memorandum was a document by George Canning (British Foreign Secretary) written in October 1823, stating that Great Britain had no intention of aiding Spain in the retention of her colonies in Latin and South America.
 The document was a result of talks with Prince Jules de Polignac, the French Ambassador to Great Britain.
 Both countries (France and Great Britain) agreed that there was no hope of Spain recovering her colonies in the Americas, that neither nation had any desire to gain territory in the region, or gain exclusive commercial treaties.
 Canning was then able to advise King George IV to extend diplomatic recognition to Buenos Aires, Colombia, and Mexico, and authorize British ministers in South America to negotiate with their respective states for commercial treaties. Earl of Hardwicke
Earl of Hardwicke is a title in the Peerage of Great Britain.
 It was created in 1754 for Philip Yorke, 1st Baron Hardwicke, Lord Chancellor of Great Britain from 1737 to 1756.
 He had already been created Baron Hardwicke, of Hardwicke in the County of Gloucestershire, in 1733, and was made Viscount Royston at the same time as he was given the earldom.
 These titles were also in the Peerage of Great Britain.
 He was succeeded by his eldest son, the second Earl.
 He represented Reigate and Cambridgeshire in the House of Commons and served as Lord Lieutenant of Cambridgeshire.
 Lord Hardwicke married Lady Jemima Campbell, only daughter of John Campbell, 3rd Earl of Breadalbane, and granddaughter and heiress of Henry Grey, 1st Duke of Kent, who succeeded her grandfather as Marchioness Grey in 1722 (a title which became extinct on her death).
 They had two daughters of whom the eldest, Lady Amabel, was created Countess De Grey in her own right in 1816.