The Anglo-Irish Treaty is signed in London by British and Irish representatives.

The 1921 Anglo-Irish Treaty, commonly known in Ireland as The Treaty and officially the Articles of Agreement for a Treaty Between Great Britain and Ireland, was an agreement between the government of the United Kingdom of Great Britain and Ireland and the government of the Irish Republic that concluded the Irish War of Independence. It provided for the establishment of the Irish Free State within a year as a self-governing dominion within the "community of nations known as the British Empire", a status "the same as that of the Dominion of Canada". It also provided Northern Ireland, which had been created by the Government of Ireland Act 1920, an option to opt out of the Irish Free State, which was exercised by the Parliament of Northern Ireland.

London is the capital and largest city of both England and the United Kingdom, with a population of 8,945,309 in 2023. Its wider metropolitan area is the largest in Western Europe, with a population of 15.1 million. London stands on the River Thames in southeast England, at the head of a 50-mile (80 km) tidal estuary down to the North Sea, and has been a major settlement for nearly 2,000 years. Its ancient core and financial centre, the City of London, was founded by the Romans as Londinium and has retained its medieval boundaries. The City of Westminster, to the west of the City of London, has been the centuries-long host of the national government and parliament. London grew rapidly in the 19th century, becoming the world's largest city at the time. Since the 19th century the name "London" has referred to the metropolis around the City of London, historically split between the counties of Middlesex, Essex, Surrey, Kent and Hertfordshire, which since 1965 has largely comprised the administrative area of Greater London, governed by 33 local authorities and the Greater London Authority.