The first Anglo-Japanese Alliance is signed in London.

The Anglo-Japanese Alliance was an alliance between the United Kingdom and the Empire of Japan which was effective from 1902 to 1923. The treaty creating the alliance was signed at Lansdowne House in London on 30 January 1902 by British foreign secretary Lord Lansdowne and Japanese diplomat Hayashi Tadasu. After the preceding era of unequal treaties enforced on Asian countries including Japan, the alliance was a military pact concluded on more equal terms between a Western power and non-Western nation. It reflected the success of Meiji-era reforms that modernized and industrialized Japan's economy, society and military, which enabled Japan to extract itself from the inferior position it had previously shared with other Asian countries like China, which had been subordinated to Western empires either through formal colonial acquisition or unequal treaties.

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.