We probably don't need to tell you that London is a very diverse city. At the time of the last census, 37 per cent of the population were foreign-born and over 250 langauages were spoken within city limits. For around 1.7 million Londoners, English is a second language.
To visualise quite how linguistically diverse the city is, Oliver O'Brien, a researcher at UCL, used 2011 census data to map the most common language besides English spoken by those living within 200m of London Underground, Overground, DLR and future Crossrail stations.
Here's central London (you see an interactive version showing the whole network at Tube Tongues):
The size of the circles represents the percentage of people who spoke the second most dominant language. To give you a rough idea, in Shadwell, the largest visible circle, 32.8 per cent of census respondants spoke Bengali.
The dominance of French in Soho, Marlybone and Mayfair is a little surprising – though, as you can see from the size of the circles, the percentages weren't actually that high (around 5 or 6 per cent); the emphasis on French in the UK education system may also have something to do with it. Bengali dominates in east London, and Arabic in west. Unsurprisingly, there's a clutch of Chinese-dominated stops around Chinatown.
In fact, language communities seem to group around certain areas: very few of the stops are dominated by a language that doesn't dominate another stop nearby.
Another trend is that, for the most part (with the notable exception of the Gujarati speakers in Willesden and Wembley) the circles tend to get smaller as you move out towards the ends of tube lines. This implies either that the city's ourskirts are less diverse, or that one language doesn't dominate. On the Central line, it seems to be the former. Here's a breakdown of the languages spoken in Epping, up at the northernmost end, compared with Leytonstone, just a few stops down:
The most linguistically diverse stop of all was Turnpike Lane in northeast London, home to 16 languages. We propose a name change to "Babel".