London is the capital of the United Kingdom and of England. It stands on the River Thames in south-east England, at the head of a tidal estuary that runs about 80 kilometres (50 miles) down to the North Sea. The 2021 census counted about 8.8 million people in Greater London, and the wider metropolitan area of roughly 15 million is the largest in Western Europe. London has been a major settlement for nearly 2,000 years, and almost everything about its shape, from the Roman walls of the City to the steel gates of the Thames Barrier, goes back to one fact: this was the lowest place where the Thames could be bridged.
A Gravel Bank at the Thames's Lowest Bridging Point
Before the Romans arrived there was no London. There were scattered Bronze Age and Iron Age settlements along the river, but no town. The Thames at that time was broader and shallower than it is now, with wide marshes. At high tide its shores could reach five times their present width.
What made the site work was firm ground on both banks. On the south side, where Southwark now stands, a narrow strip of higher ground ran north to south through a maze of marshy tidal islands, and even at high tide it left a much narrower stretch of water to cross. On the north side, firm ground climbed to a low hill, the present Cornhill. There was probably a ford somewhere in this reach. Here the river was narrow enough for a bridge but still deep enough for the seagoing ships of the day, which made it the natural place for both a port and a crossing.
The Romans, who invaded Britain in AD 43, saw this quickly. Their town, Londinium, was founded around AD 47 to 50. A port was built between 49 and 52. A timber bridge followed around AD 50, the first of many London Bridges. Roads from across the new province converged on it, which is why London became a road hub before it was a capital.
Cornhill, Ludgate Hill and the Walbrook: Londinium's Two Hills
Londinium was built on two low hills on the north bank, Cornhill to the east and Ludgate Hill to the west, with a small stream, the Walbrook, running between them into the Thames. Its waterfront ran for about 1.5 kilometres, from around Ludgate Hill to where the Tower of London stands today. Early Londinium covered only about 1.4 square kilometres, roughly half the area of the modern City of London.
After Boudica's Iceni burnt it in AD 60 or 61, it was rebuilt, and by the 2nd century it had replaced Colchester as the main city of the province of Britannia. At its height it may have held between 30,000 and 60,000 people, and its forum basilica on Cornhill was one of the largest buildings north of the Alps when the emperor Hadrian visited in 122.
Between about 190 and 225 the Romans built a wall around the landward side of the city. That wall lasted for roughly 1,600 years and still broadly marks the edge of the City of London, the square mile that is now the financial district. A modern street in the City is still called London Wall. The two hills kept their roles too. Sir Christopher Wren's St Paul's Cathedral, completed in 1710 after the Great Fire of 1666, crowns Ludgate Hill, while the Bank of England and the Royal Exchange sit near the Walbrook valley.
Thorney Island and the Move Upstream to Westminster
When Roman rule collapsed in the early 5th century, the walled city was largely abandoned. Later an Anglo-Saxon trading settlement called Lundenwic grew up about a mile to the west, just north of the present Strand; it was established by the early 7th century. Viking raids, frequent from the 830s, ruined it, and in 886 Alfred the Great "refounded" London inside the old Roman walls, which were easier to defend.
London's second centre grew on another piece of river geography. Further upstream, the River Tyburn split into rivulets as it reached the Thames and formed a small island, Thorney Island. It may once have been part of a ford used by Watling Street. Monks settled there, and Edward the Confessor rebuilt its abbey in grand Romanesque style. William the Conqueror was crowned in the new Westminster Abbey on Christmas Day 1066, and in 1097 William II began Westminster Hall beside it, the core of the Palace of Westminster.
Through the 12th and 13th centuries the royal government, which had followed the king around the country, settled more and more at Westminster. Winchester had been the capital of Anglo-Saxon England, but it could not match the wealth of London. The result was a capital with two hearts: Westminster for the crown and later Parliament, and the City for money and trade, each with its own administration. The island itself has vanished. Its streams were built over, the ground level rose and the river was walled in, so the Houses of Parliament now stand on dry land.
Old London Bridge and the Pool of London
For most of the Middle Ages the bridge was London. After the murder of Thomas Becket, who was born at Cheapside, Henry II ordered a stone bridge with a chapel to the martyr at its centre. Work began in 1176 under Peter of Colechurch and was finished in 1209. The bridge was about 282 metres long and stood on nineteen piers linked by arches and a wooden drawbridge.
Old London Bridge stood for more than 600 years, until 1831, and it shaped the port. Its narrow arches blocked large ships, so sea-going vessels stopped below it in the stretch called the Pool of London, loading at quays in the City and Southwark. Until Putney Bridge opened in 1729, London Bridge was the only road crossing of the Thames downstream of Kingston.
Buried Rivers and Bazalgette's Embankments
Smaller streams such as the Fleet, the Tyburn, the Walbrook and the Effra ran down from the hills north and south of the valley. The Fleet, the largest, rises in the ponds on Hampstead Heath. Its name comes from the Old English word for a tidal inlet, and in Anglo-Saxon times it served as a dock. It gave its name to Fleet Street. As the city grew, these streams became open sewers and were covered over one by one.
By the 1850s the sewers emptied straight into the Thames. Cholera killed 14,000 Londoners in 1848, and in the hot July and August of 1858 the smell from the river, the Great Stink, became so bad that Parliament finally acted. The engineer Joseph Bazalgette built a network of intercepting sewers, running west to east and carrying waste to outfalls downstream of the city. Work lasted from 1859 to 1875. About 132 kilometres of main intercepting sewers were fed by some 1,800 kilometres of new street sewers.
To fit the low-level sewer through central London, Bazalgette narrowed the river itself. The Victoria Embankment on the north bank, begun in 1862, holds the sewer, an underground railway and a wide road behind a granite wall. Together the scheme reclaimed about 22 acres of land from the Thames, and it gave central London the straight, walled river it has today. The Fleet still flows, but as a sewer beneath Farringdon Street.
Eleven Miles of Docks, From West India Dock to Canary Wharf
As trade grew, the open quays of the Pool of London could not cope. The answer was to dig enclosed docks into the marshes east of the City, low-lying land that was poor for farming and lightly populated. The West India Docks opened in 1802, followed by the London Docks in 1805, St Katharine Docks in 1828 and the Royal Victoria in 1855. In the 18th and 19th centuries the Port of London was the busiest in the world, with wharves stretching for about 18 kilometres (11 miles) along the river.
Each dock specialised: the Surrey Docks in timber, Millwall in grain. The docks employed armies of lightermen, porters and casual labourers, who filled the East End. London was the world's largest city from about 1831 to 1925.
The end came with the shipping container. Container ships were too big for the old basins, and trade moved downstream to deep-water ports such as Tilbury and Felixstowe. Between 1960 and 1980 every one of London's docks closed, leaving about 21 square kilometres of derelict land. In 1981 the government set up the London Docklands Development Corporation, and the West India Docks became the site of Canary Wharf, a second business district to rival the City of London.
Teddington to Woolwich: Living With a Tidal River
The Thames through London is tidal. Its usual tidal limit is Teddington Weir, in the south-west of the city, the lowest weir on the river. Below it, the water rises and falls twice a day, and that has always made London vulnerable to floods.
The North Sea flood of 1953 hit parts of the Thames Estuary and London, and it led to a search for a way to close the river against a storm surge. A surge happens when a deep depression tracks across the North Sea and meets a high spring tide. Winds can then drive water up the estuary as much as 3.5 metres above normal. Unchecked, such a surge could flood 117 square kilometres of London.
The solution was the Thames Barrier at Woolwich, about 3.2 kilometres east of the Isle of Dogs, between Silvertown on the north bank and New Charlton on the south. It has been operational since 1982. Its hollow steel gates, the four largest 20.1 metres high, rest in sills on the river bed and rotate upward to close the river when a surge is forecast. The barrier was expected to close two or three times a year, but by the mid-2000s it was closing six or seven times a year, and in the very wet winter of 2013 to 2014 it closed 50 times.
London is a city that grew outward from a river crossing: its financial district sits inside a Roman wall and its Parliament on a vanished island. Since 1965 the metropolis has been governed as Greater London, a region of 1,583 square kilometres made up of 32 boroughs and the City, now led by the Greater London Authority and its mayor. The national institutions that sit at Westminster are explained in our guide to the government of the United Kingdom. To follow the river from its source in the Cotswolds to the sea, read the complete guide to the River Thames, and for the fortress William the Conqueror built on the edge of the Roman city, see our guide to the Tower of London.
Quick Facts About London
- Country: United Kingdom
- Continent: Europe (Western Europe)
- Country population: approximately 69.9 million
- Capital city status: London is the capital of United Kingdom, the seat of national government, and the location of foreign embassies, parliament, and the head of state's official residence.
Frequently Asked Questions
What is the capital of United Kingdom?
The capital of United Kingdom is London. London is the seat of national government, hosts most foreign embassies and consulates, and is typically where the head of state and parliament are located.
What continent is London in?
London, the capital of United Kingdom, is located in Europe, in the Western Europe region. As United Kingdom's capital, London serves as the country's primary connection to the broader Europen political, economic, and cultural sphere.
Why is London the capital of United Kingdom?
London was chosen as the capital of United Kingdom for reasons that typically combine geography, history, and politics. Capital city selections often reflect a desire for centrality (being accessible from across the country), historical importance (being a longstanding seat of government or culture), or neutrality (being acceptable to multiple regions or ethnic groups within the country). The specific reasons for London's designation are detailed in the city's history above.
What is London known for?
As the capital of United Kingdom, London is best known for housing the country's central government institutions — parliament, presidential or royal residences, supreme court, and key ministries. It is also typically a major cultural and economic center within United Kingdom, hosting national museums, embassies, and signature monuments. The introduction and history sections above provide detailed coverage of the city's specific notable institutions and landmarks.
Related Pages
- United Kingdom Country Guide — full geography, climate, economy, and culture overview
- Flag of United Kingdom — meaning, history, and design of United Kingdom's national flag