London

Overview

London is the capital of the United Kingdom and its largest city, a metropolis of about 9.1 million people on the River Thames in southeastern England, governed by a directly elected Mayor and the London Assembly and run day to day by 32 boroughs plus the City of London (Britannica; Office for National Statistics; Local Government Chronicle). Founded by the Romans as Londinium in 43 CE, it is among the oldest of the world’s great cities, with a history spanning nearly two millennia, and today it is Britain’s economic, transportation and cultural centre (Britannica).

London sits astride the Thames some 50 miles (80 km) upstream from its estuary on the North Sea, inside a Green Belt of open land with the M25 motorway threaded around it at a radius of about 20 miles (30 km) from the city centre (Britannica). Its physical limits more or less match the boundaries of Greater London, the metropolitan county formed in 1965, which covers 607 square miles (1,572 square km) (Britannica). The historic counties around it — Kent, Surrey and Berkshire to the south of the river, Buckinghamshire, Hertfordshire and Essex to the north — extend beyond their current administrative counties to include substantial parts of Greater London (Britannica).

From Londinium to a global capital

London’s founding can be traced to 43 CE, when Roman armies began their occupation of Britain under Emperor Claudius and established a settlement they called Londinium at a point just north of the marshy Thames valley, where two low hills were sited (Britannica). The first definite mention of London occurs in 60 CE, by the Roman historian Tacitus (Britannica). A thousand years later, the Norman Conquest stamped the city again: William the Conqueror built the White Tower in 1066 as a demonstration of Norman power, sited strategically on the Thames to act as both fortress and gateway to the capital (UNESCO). The Tower went on to foster several of England’s major state institutions, covering defence, record-keeping and coinage, and it was the setting for the execution of three English queens (UNESCO).

Disaster has repeatedly remade the city. The Great Fire of London, from 2 to 5 September 1666, began accidentally in the house of the king’s baker in Pudding Lane near London Bridge and destroyed a large part of the City of London, including most of the civic buildings, old St Paul’s Cathedral, 87 parish churches and about 13,000 houses (Britannica). Christopher Wren’s great work in the aftermath was the erection of a new St Paul’s Cathedral and many churches ranged around it, while the Monument, a column erected in the 1670s near the source of the blaze, still commemorates the fire (Britannica). During the Second World War, London suffered intense aerial bombardment by Nazi forces during the Blitz, a campaign from September 1940 to May 1941 in which an estimated 43,000 Londoners died, a further 50,000 were injured, and more than 70,000 buildings were destroyed (Britannica).

Victorian London added the innovation that most changed how a great city could work: on 10 January 1863 the world’s first underground railway opened as the Metropolitan Railway, running between Paddington and Farringdon (Rail Technology Magazine). The growth of the built-up area was later halted by strict town planning controls in the mid-1950s, and the Green Belt has contained the metropolis ever since (Britannica). In 2000, city-wide government was restored with the creation of a Mayor of London and a London Assembly, a reform that became the prototype for contemporary city-regional governance models (Local Government Chronicle).

How London is governed

The Greater London Authority (GLA) comprises the Mayor of London and the London Assembly (Greater London Authority). The GLA has five functional bodies, overseeing transport, policing, fire and rescue services and regeneration, which together form the GLA Group (Greater London Authority). Its wider work covers housing, the environment, planning, skills, resilience, culture, health and economic development (Greater London Authority). The Mayor in office at the Tube’s 160th anniversary in 2023 was Sadiq Khan (Rail Technology Magazine).

Below the GLA sit the boroughs. In 1965, 32 boroughs were created, and the City of London was retained with all the powers of a borough, though also keeping its own police force and other unique characteristics (Local Government Chronicle). The arrangement is two-tier: the GLA handles strategic, London-wide functions, while the boroughs and the City handle local services (Local Government Chronicle). London’s position in the English constitution is distinctive in one more way: the UK Government started to devolve powers within England in 2000 through the establishment of the Greater London Authority — yet English devolution involves no law-making or tax-raising powers, unlike devolution to Scotland, Wales and Northern Ireland (UK Cabinet Office).

Body	Role	Scope
Mayor of London	Executive head of the GLA	Strategic, London-wide functions
London Assembly	Scrutiny of the Mayor	Holds the Mayor to account
Transport for London	Transport	Functional body of the GLA Group
Mayor’s Office for Policing and Crime / Metropolitan Police	Policing	Functional body of the GLA Group
London Fire Commissioner	Fire and rescue	Functional body of the GLA Group
32 boroughs + City of London	Local services	Local tier beneath the GLA

Sources: Greater London Authority; Local Government Chronicle.

People, money and the railway north

London’s population stood at about 9.1 million in 2024 on the ONS regional accounts basis, up from the 8,173,941 recorded in the preliminary 2011 census figure carried by Britannica — the gap reflects more than a decade of growth, not a disagreement between sources (Office for National Statistics; Britannica). Spread across Greater London’s 1,572 square km, that is roughly 5,800 people per square km, a density produced by dividing the ONS population by the Britannica area (Office for National Statistics; Britannica). London is by far Britain’s largest metropolis, and its cosmopolitan population is one of the features Britannica stresses most about the city (Britannica).

The economy matches the scale: in 2024 London’s GDP was £656,291 million, with GDP per head of £72,201 — the highest of any UK country or region — and real GDP growth of 1.3% (Office for National Statistics). That per-head figure is roughly 73% above the UK average of £41,627, a gap that reflects both the concentration of high-value work in the capital and the commuting flows the ONS warns can distort per-head comparisons (Office for National Statistics). London is the country’s economic, transportation and cultural centre, and the Tube — the world’s first underground railway, opened in 1863 — remains the spine of how its people move (Britannica; Rail Technology Magazine).

London’s railways also tie it to the rest of England, which is why a crash in Leicestershire could disrupt the capital. On 1 February 2008, at Barrow upon Soar in Leicestershire, the 06:13 Nottingham to Norwich train collided with debris from a footbridge demolished by a tipper lorry’s raised body and derailed (RAIB). The Midland Main Line remained blocked, with services from London terminating at Leicester, until engineers reopened two of the four lines in the early hours of the following day (Rail Technology Magazine). The episode is covered in full in the profile of the Barrow upon Soar rail crash.

Measure (2024 unless stated)	London	United Kingdom
Population	9.1 million	69.3 million
GDP	£656,291 million	£2,884,006 million
GDP per head	£72,201	£41,627
Real GDP growth	1.3%	1.1%

Sources: Office for National Statistics for population and GDP; Britannica for London’s area.

Frequently asked questions

Is London the capital of England or of the United Kingdom? Both. London is the capital of the United Kingdom and also the capital and largest city of England, its largest constituent nation. The UK Parliament, the UK Government and the monarch are all based in London, which is why the city is the seat of government for both England and the whole UK.

How is London governed? London has two tiers. The Greater London Authority — the Mayor of London plus the London Assembly — handles strategic, London-wide functions through bodies covering transport, policing, fire and rescue and regeneration. Beneath it, 32 boroughs and the City of London run local services, with the City keeping its own police force.

How many people live in London? About 9.1 million, on the ONS regional accounts basis for 2024. That is up from 8,173,941 in the preliminary 2011 census figure carried by Britannica. No mid-2025 London-specific estimate was verified from a fully-read source for this profile, so the 2024 figure is used throughout.

What is the world’s first underground railway? The London Underground, opened on 10 January 1863 as the Metropolitan Railway between Paddington and Farringdon. It is still known as the Tube, and its 160th anniversary was marked in 2023 with the Mayor of London, Sadiq Khan, meeting long-serving Underground staff at Baker Street station.

What this profile does not claim

• It does not give a mid-2025 London population figure; the 9.1 million used here is the ONS regional accounts figure on a mid-2024 population basis.
• It does not state a death toll for the Great Fire of 1666; the Britannica article read in full gives the scale of destruction but no death toll.
• It does not give Tube ridership, fare or line-by-line figures, which no fully-read source verified in this pass.
• It does not state the Mayor of London’s party affiliation or the composition of the London Assembly.
• It does not describe the Barrow upon Soar crash in full; it records only the disruption to London services, and points to the dedicated crash profile for the accident itself.