Do the Indian and Bangladeshi communities have different customs regarding surnames that would lead to a more homogenous naming. Because the results seem disproportionate and shrink massively if you move the slider to the 2nd most popular name or further.

The map is actually a reasonably accurate reflection of where the largest communities of Asian British and South Asian immigrants live.

That said, whether it's disproportionately common amongst Indian ethnic groups or otherwise, you won't meet that many Patels even in the relevant parts of London. To put things into perspective, the population of Greater London is ~7 million, and there are <100,000 Patels in the entire UK sources: http://gbnames.publicprofiler.org/Statistics.aspx?name=PATEL... http://www.telegraph.co.uk/news/uknews/5040755/Britains-most...

If you want a better picture of the relative sizes of UK ethnic groups by district (amongst many other demographic factors) then the interactive map at www.censusprofiler.org is awesome.

Informally, that seems to be true. See Patel: http://en.wikipedia.org/wiki/Patel

See if you can spot the Cohen island in N-NW London. I lived in that area for a bit, and around Golders Green and Stamford Hill there's a large Jewish community, many of them orthodox.

This beautifully illustrates Thomas Schelling's racial segregation model, for which he coined the term "Tipping Point" 30 years before Malcolm Gladwell popularized it:

Schelling, T. (1969). Models of segregation. The American Economic Review, 59(2), 488-493

(Schelling won the Nobel Prize in economics in 2005)

A time based view would be interesting.

The next generation moves away form these ghettos and assimilates into the rest of London, after a few generations there are only hotspots of the original immigrants left in these places and then usually only if there are strong religous reasons.

If you go into London through the east end (Brick lane etc) the names of pubs are Huguenot (from early 1800s) then there are names of Jewish merchants and tailors on the top floors of buildings (from the early 1900s) then the ground floor is now Bangladeshi.

For the Netherlands:

- by last name: http://www.meertens.knaw.nl/nfb/index.php?taal=eng

- by first name: http://www.meertens.knaw.nl/nvb/english

Most of it is Dutch only, but both have historical data (the one for first names in particular is nice)

Is there any significance to the distribution of the "Welsh" names? They appear a bit more central, but not especially. Perhaps at one time they were the poorer, more centrally located 'immigrants', but have since spread out?

Difficult to draw too many conclusions from that since whilst Jones and Williams are more common in Wales, the vast majority of British people with those surnames are English. Jones and Williams are the second and third most popular names in most of the outer suburbs too. If there's any pattern here it's more likely to be the reverse; the density of very English Smiths is much greater in the outer suburbs.

The nationalistic Welsh will tell you they are the real british people, but displaced and pushed westwards (into what is now Wales) by the Romans, Normans, Anglo Saxons etc. So a name might be mostly Welsh now, but the people with that name might have lived in that area for a very long time,

I'm not sure about this - first-century London was about the size of Hyde Park!

http://en.wikipedia.org/wiki/Roman_London#First_century_AD

Edit - also, it appears that prior to the fifteenth century, the Welsh tended to use a patronymic naming system.

http://en.wikipedia.org/wiki/Welsh_surnames

In the 15thC a Welshman took the throne of England (Henry VII) and brought a lot of fellow countrymen into court with him, so they needn't have been poorer immigrants

Welsh predates english by centuries, in terms of lineage. Most of europe once spoke celtic languages that are most closely connected to welsh.

I'd guess it's because the welsh has a head start on migration of a few hundred years over the other groups on the chart.

Fascinating, but not especially surprising. Some references to eg major roads or borough boundaries would be really useful!

The boundaries in the map are borough boundaries.

I found it interesting that a couple of zoom levels down, you can see a big cluster of Irish names on the Brent side of the Kilburn High Road, and another in W7.