London began as a Roman settlement in AD 43, where the City, our financial district, stands today, and flourished as a market town for the next 350 years. The most visible legacy from this era is the straight roads that led out of Londinium, as it was then known, which now form some of the capital's main arteries - Oxford St, Edgware Rd, Kingsland Rd. At the Museum of London itself you can also view part of the Roman wall and artifacts unearthed in the City.

After the Romans left in AD 410, the town declined. The Anglo Saxons who settled in the region were farmers living in small communities. But, by AD 800, London was a bustling trade centre again.

The town's strategic and commercial importance grew and it was fought over by Vikings and warring Saxon factions before falling into the hands of William the Conqueror in 1066. Under his reign, the Tower of London was built to protect the city.

During the next five centuries, London became a great, dense, medieval city of timber-framed buildings towering over narrow, winding streets, with gothic churches and cathedrals. It also became a city of slums, squalor and disease. The Black Death, halving the population of the city in 1348, and the Great Plague of 1665, claiming 100,000 lives, are only the most extreme examples of frequent epidemics that swept the city. Rich citizens were able to escape the filth and moved to the greener outskirts, thus expanding the West End.

Under the reign of Elizabeth I (1558-1603), the arts flourished and Bankside became London's first theatreland; it was here that Shakespeare's Globe Theatre stood, and the Bard's plays staged. The region was home to the low-life, who thrived in brothels and taverns.

But these establishments were shut down after the defeat of the monarchy in the English Civil War (1648), which brought in an era of puritanism. Only after the restoration of the monarchy, in 1660, were theatres tolerated again. The Theatre Royal, Covent Garden, was built, marking the beginning of the West End as an entertainment district.

Medieval London ceased to exist on 2 September 1666 when a fire in Pudding Lane destroyed over three-quarters of it. A law was passed requiring new structures to be stone, and the entire character of the City was changed, though the quirky street patterns remain even now.

But there are a few ancient relics that survived the flames. You can imagine what an Elizabeth street would have looked like from a glimpse at Staple Inn (High Holborn, WC1), with its protruding upper storeys, or Prince Henry's Room (17 Fleet St, EC4). Nearby Middle Temple Hall with its oak hammerbeam roof and Temple Church (open daily) are two other notable survivors.

In the midst of the raging conflagration was the Guildhall (off Gresham St, EC2), which was able to withstand the flames because it was partially in stone. Also protected by stone were the Tower Green Tudor houses, safely within the fortified walls of the Tower of London and accessible on a tour there.

The change in the character of the City can perhaps best be understood by a visit to St Paul's Cathedral, built after the fire destroyed the gothic cathedral that stood in its place - models of which are on display in the museum located under the Cathedral (EC4).

In the 18th and 19th centuries, London mushroomed as a commercial centre; docks, bridges and canals were built and, in 1836, the first railway opened, forming the infrastructure that allowed England's industrial revolution to gather pace. Reacting against such progress, architects sought refuge in England's medieval past and many public buildings (the new Houses of Parliament) were done in gothic style.

By the start of the 20th century, London was a huge metropolis, but wartime devastation and depression took their toll. Development since then has seen the re-emergence of the South Bank as a centre for the arts and the regeneration of Covent Garden (once home to fruitsellers) into a shopping area with piazzas, street cafés, buskers and boutiques.

But it's the former docks which now form the focus for growth (go here on the Docklands Light Railway) and may be responsible for turning the capital into a linear city. Once again, London is changing shape, but visitors continue to come and many return. As Moore said: "Go where we may, rest where we will, eternal London haunts us still."