This is what we found on Wikipedia regarding the Sherlock Holmes Museum tickets & Westminster Highlights Walking Tour:

London is the capital and largest city of England and the United Kingdom, with a population of 9.1 million people in 2024. 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 site of the national government and parliament for centuries. 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 among the counties of Middlesex, Essex, Surrey, Kent and Hertfordshire. Since 1965 it has largely comprised the administrative area of Greater London, governed by 33 local authorities and the Greater London Authority.

As one of the world's major global cities, London exerts a strong influence on world art, architecture, culture, cinema, entertainment, commerce, finance, education, healthcare, media, science, technology, tourism, transport and communications. London is Europe's largest city economy and one of the world's major financial centres. London is home to several of the world's leading academic institutions and hosts Europe's largest concentration of higher education institutions, comprising over 50 universities and colleges collectively enrolling more than 500,000 students in 2023. It is the most-visited city in Europe and has the world's busiest city airport system. The London Underground is the world's oldest rapid transit system.

London's diverse cultures encompass over 300 languages. The 2025 population of Greater London of just over 9.8 million made it Europe's third-most populous city, accounting for 13.1 per cent of the United Kingdom's population and 15.5 per cent of England's population. The Greater London Built-up Area is the fourth-most populous in Europe, with about 9.8 million inhabitants as of 2011. The London metropolitan area is the third-most-populous in Europe, with about 15 million inhabitants as of 2025, making London a megacity.

Landmarks include the Tower of London, Westminster Abbey, Buckingham Palace, the London Eye, Piccadilly Circus, St Paul's Cathedral, Tower Bridge and Trafalgar Square. The city has the most museums, art galleries, libraries and cultural venues in the UK, including the British Museum, the National Gallery, the Natural History Museum, Tate Modern, the British Library and numerous West End theatres. Annual sporting events include the FA Cup Final (held at Wembley Stadium), the Wimbledon Tennis Championships and the London Marathon. It became the first city to host three Summer Olympic Games upon hosting the 2012 Summer Olympics.