“THIS is a Christian country,” David Cameron declared valiantly, during an Easter speech in 2015. Not, perhaps, for much longer. In 2001 40.1m Britons declared themselves Christian on the census form; in 2011, the figure was just 36.1m, or 59% of the population. Yet some places are resisting the tide of godlessness. According to a new analysis* of census data, Britain’s bastions of Christianity tend to be urban (“but not too urban”) and mostly in north-west England. In Knowsley, an otherwise unremarkable borough on the outskirts of Liverpool, four out of five people were self-professed Christians in 2011; in nearby Chorley, Halton and West Lancashire, about three out of four were.

Catholics originally hailing from Ireland account for much of the concentration in England’s north-west, says Peter Brierley, a church statistician. This group tends to pass religion on to its children, and to identify with it strongly enough to tick the optional box on the census. Like most second- or third-generation immigrants, he says, they tend to live just outside cities. Between 2001 and 2011 the north-west saw relatively little change in the number of Christians: Irish immigrants tend to be traditionally working class, says Mr Brierly: “They move, at most, one street over” and, like Britain’s Muslim and Jewish populations, Catholics cluster rather than spread.

Christians are scarcest in London, particularly north of the Thames, where fewer than 50% declared themselves Christian in 2011. Here, other religions crowd in: 34.5% of people in Tower Hamlets, and 32% in Newham, are Muslim (against a national figure of 4.8%); 25.3% of those in Harrow, and 17.8% in Brent, are Hindu (versus just 1.5% nationally).