Events from the year 1820 in the United Kingdom. This year sees a change of monarch after a nine-year Regency. Incumbents Monarch – George III (until 29 January), George IV (starting 29 January) Regent – George, Prince Regent (until 29 January) Prime Minister – Robert Jenkinson, 2nd Earl of Liverpool (Tory) Foreign Secretary – Robert Stewart, Viscount Castlereagh Parliament – 6th (until 29 February), 7th (starting 21 April) Events 8 January – General Maritime Treaty ("General Treaty for the Cessation of Plunder and Piracy by Land and Sea, Dated February 5, 1820") signed between the sheikhs of Abu Dhabi, Sharjah, Ajman, Umm Al Quwain and Ras Al Khaimah (later constituents of the Trucial States) in the Arabian Peninsula and the United Kingdom. 29 January – George IV of the United Kingdom ascends the Throne on the death at Windsor Castle of his father George III (after 59 years on the throne), ending the period known as the Regency era which began in 1811. George IV has served as prince regent during this time due to his father's mental deterioration. The title Prince of Wales falls into abeyance for 21 years. 30 January – Royal Navy captain Edward Bransfield in the Williams is the first person to positively identify Antarctica as a land mass. 23 February – a plot to murder the Cabinet, the Cato Street Conspiracy, is exposed. 10 March – Astronomical Society of London is founded. 1–2 April – a Proclamation, signed "By order of the Committee of Organisation for forming a Provisional Government", is distributed in the Glasgow area, beginning the "Radical War" in Scotland. The following day, around 60,000 – particularly weavers – stop work across a wide area of central Scotland. Disaffection spreads to the West Riding of Yorkshire. 5 April – Radical War: Troops capture radicals at Bonnybridge. 8 April – Radical War: Radical prisoners from Paisley are freed from jail in Greenock after militia have killed eight of the crowd. 14 April – 1820 United Kingdom general election, begun on 6 March, concludes with an increased Tory party majority. 1 May – the Cato Street conspirators are the last to suffer judicial decapitation in the UK following their public hanging for treason outside Newgate Prison in London (legally, a mitigation of the last sentence in Britain of hanging, drawing and quartering). 11 May – launch of , the ship that will take the young