You might think you know London – Western Europe’s largest city and a powerhouse of commerce, fashion and culture. But the UK's capital has always had a complex personality. Ask six people what London is and you’ll get a dozen different answers. So how do you define London?

London: undeniably grand, surprisingly hard to pin down. Image by Vladimir Zakharov / Getty

How London began

The Celts might have got the ball rolling: according to 12th-century writer of myth and history Geoffrey of Monmouth, the Celtic King Lud founded the town, modestly naming it Caer Lud or Kaerlundein. It’s certainly true that the area we now know as London was inhabited millennia ago – ancient relics have been unearthed at sites including Southwark, south of the River Thames.

It wasn’t until the Romans founded the port of Londinium on the north bank of the Thames in AD 43 that a permanent population arrived. Five centuries later the Saxons took over the reins of Lundenwic, basing themselves west of the old Roman city walls. But those first three settlements weren’t even in the same place – they were different proto-Londons.

And it’s still confusing: many visitors never even set foot in the true City of London – the legal and commercial centre based around the site of the old Roman settlement. The majority of the attractions of the West End – museums, galleries, theatres and shops – lie in the City of Westminster, west of the Temple Bar Memorial on Fleet St that divides the two central boroughs.

So: London is the combined City of Westminster and City of London? Well, that’s not the whole story. Even seven centuries ago, overflow was spreading south of the Thames, outside both cities.

London's shifting centre

How far out does London reach? First you need to find its true centre.

It could be the London Stone, an unprepossessing lump of rock on Cannon St that's reputedly the point from which distances were measured in Roman Britain. Yet today road distances to and from London are measured from nearby Charing Cross. When London’s postal districts were first demarked in 1856, meanwhile, they were set at a radius of 12 miles (19km) from the post office at St Martin’s Le-Grand, near St Paul’s Cathedral. That gives another definition of the city: districts that have the London postcodes laid down in 1856 and tweaked afterwards (NW for northwest London, SE for southeast and so on).

Except that doesn’t work, either: when the administrative region of Greater London was created in 1965 it stretched beyond the Royal Mail’s London postcodes.

That administrative definition has problems of its own. For example, Biggin Hill is in the London Borough of Bromley – but really, it’s too rural. Can spots called Pratt’s Bottom, Jewels Wood and Leaves Green truly be in the capital?

Trains & automobiles

London Underground (the ‘tube’) is the quintessential transport network. So everywhere in the city is on the tube? Not even close – by that measure none of southeast London makes the grade.

Some say the capital’s limits are bound by the M25, its main ring road. Clearly nonsense: Abbots Langley, Titsey, Stoke D’Abernon – all within the M25, and none of them actually connected with London.

Then it must be the people – over seven million of them. The old definition of cockneys was those born within the sound of the church bells of St Mary-le-Bow, but since it’s now surrounded by offices, hardly anyone lives near enough to hear them.

In truth, London isn’t defined by trains or postcodes – it’s a state of mind. Ask a stranger in the street if they’re a Londoner. If they say yes, you’re likely in the capital.

And if they ignore you completely and march on, it’s a dead certainty. You’re in London.

This article was first published in August 2011 and updated by Sally Schafer in April 2015.

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