The Muslim population has grown from 1.65 million to 2.87 million since 2001, say researchers. What does this mean for liberal Britain?

There is a remarkable statistic in today's main Daily Telegraph leader:

The Pew Forum on Religion and Public Life estimates that there are 2,869,000 Muslims in Britain, an increase of 74 per cent on its previous figure of 1,647,000, which was based on the 2001 census. No demographic statistics are reliable in an era of open borders, but such an expansion is unprecedented.

The figure of 2.87 million was first published by Pew in a little-noticed press release last September, announcing a report on Muslim Networks and Movements in Western Europe. The Pew Centre, based in Washington DC, is one of the most respected demographic research bodies in the world; its methodology is scrupulous and its approach non-partisan. The new total for British Muslims means that, so far as this country as concerned, Pew's major 2009 report Mapping the Global Muslim Population is already spectacularly out of date. Here's a map showing the updated distribution of the Muslim population in Europe:

The material about global Islam in the 2010 report is fascinating, but it's the revision of British figures that took me by surprise. Why was it not more widely reported in the autumn? And what are the implications for society? For an analysis that puts the statistics in context, let me recommend this article from the British Religion In Numbers website, which makes the point that the 2001 figure was probably an underestimate.

Pew’s UK figure for 2010 is 2,869,000, which is equivalent to 4.6% of the population. In absolute terms, the UK has the third largest Muslim community on the continent, after Germany (4,119,000) and France (3,574,000).
In percentage terms, the UK is in ninth position, after Belgium (6.0%), France, Austria and Switzerland (5.7%), The Netherlands (5.5%), Germany (5.0%), Sweden (4.9%) and Greece (4.7%). UK Muslims account for 16.8% of all Muslims in Western Europe.

There have been other indications of a dramatic increase in the numbers of British Muslims: the UK Labour Force Survey recorded a rise from 1,870,000 in 2004 to 2,422,000 in 2008. So Pew's findings aren't unsupported by independent data. Common sense suggests explanations for the increase: a high Muslim birth rate and large-scale immigration. But I'm not sure that common sense tells us what this demographic earthquake means in practice for British public life.