On 14 June 2017, a high-rise fire broke out in the 24-storey Grenfell Tower block of flats in North Kensington, West London, at 00:54 BST. 72 people died, including two who later died in hospital, with more than 70 others being injured and 223 people escaping. It was the deadliest structural fire in the United Kingdom since the 1988 Piper Alpha oil-platform disaster and the worst UK residential fire since World War II.

The fire was started by an electrical fault in a refrigerator on the fourth floor. It spread rapidly up the building's exterior, bringing fire and smoke to all the residential floors. This was due to the building's new cladding and the external insulation, since the air gap between them enabled the stack effect. The fire burned for about 60 hours before finally being extinguished. More than 250 London Fire Brigade firefighters and 70 fire engines from stations across London were involved in efforts to control the fire and rescue residents. More than 100 London Ambulance Service crews on at least 20 ambulances attended the scene, joined by specialist paramedics from the Ambulance Service's Hazardous Area Response Team. The Metropolitan Police and London's Air Ambulance also assisted the rescue effort.

The Grenfell Tower Inquiry began on 14 September 2017 to investigate the causes of the fire and other related issues. Findings from the first report of the inquiry were released in October 2019 and addressed the events of the night. It affirmed that the building's exterior did not comply with regulations and was the central reason why the fire spread, and that the fire service were too late in advising residents to evacuate. A second phase to investigate the broader causes began on the third anniversary in 2020.

As of June 2020, the fire is currently being investigated by the police, a public inquiry, and coroner's inquests. Among the issues being investigated are the management of the building by the Kensington and Chelsea London Borough Council and Kensington and Chelsea TMO (or KCTMO, which was responsible for the borough's council housing) and the responses of the Fire Brigade, the council and other government agencies. In the aftermath of the fire, the council's leader, deputy leader and chief executive resigned, and the council took direct control of council housing from the KCTMO. The national government commissioned an independent review of building regulations and fire safety, which published a report in May 2018. Across the UK and in some other countries, local governments have investigated other tower blocks to find those that have similar cladding. Efforts to replace the cladding on these buildings are ongoing.

London is the capital and largest city of England and the United Kingdom. It stands on the River Thames in south-east England at the head of a 50-mile (80 km) estuary down to the North Sea, and has been a major settlement for two millennia. The City of London, its ancient core and financial centre, was founded by the Romans as Londinium and retains boundaries close to its medieval ones. Since the 19th century, "London" has also referred to the metropolis around this core, historically split between the counties of Middlesex, Essex, Surrey, Kent, and Hertfordshire, which largely comprises Greater London, governed by the Greater London Authority. The City of Westminster, to the west of the City of London, has for centuries held the national government and parliament.

London, as one of the world's global cities, exerts strong influence on its arts, commerce, education, entertainment, fashion, finance, health care, media, tourism, and communications, and has sometimes been called the capital of the world. Its GDP (€801.66 billion in 2017) makes it the biggest urban economy in Europe, and it is one of the major financial centres in the world. In 2019 it had the second-highest number of ultra high-net-worth individuals in Europe after Paris and the second-highest number of billionaires of any city in Europe after Moscow. With Europe's largest concentration of higher education institutions, it includes Imperial College London in natural and applied sciences, the London School of Economics in social sciences, and the comprehensive University College London. The city is home to the most 5-star hotels of any city in the world. In 2012, London became the first city to host three Summer Olympic Games.London's diverse cultures encompass over 300 languages. The mid-2018 population of Greater London of about 9 million made it Europe's third-most populous city, accounting for 13.4% of the population of the United Kingdom. Greater London Built-up Area is the fourth-most populous in Europe, after Istanbul, Moscow and Paris, with about 9.8 million inhabitants at the 2011 census. The London metropolitan area is the third-most populous in Europe after Istanbul's and Moscow's, with about 14 million inhabitants in 2016, granting London the status of a megacity.

London has four World Heritage Sites: the Tower of London; Kew Gardens; the combined Palace of Westminster, Westminster Abbey, and St Margaret's Church; and also the historic settlement in Greenwich, where the Royal Observatory, Greenwich defines the Prime Meridian (0° longitude) and Greenwich Mean Time. Other landmarks include Buckingham Palace, the London Eye, Piccadilly Circus, St Paul's Cathedral, Tower Bridge and Trafalgar Square. It has numerous museums, galleries, libraries and sporting venues, including the British Museum, National Gallery, Natural History Museum, Tate Modern, British Library and West End theatres. The London Underground is the oldest rapid transit system in the world.