Just because Britain has been devout in the past doesn't mean it is so now. There are cultural values that exist now that didn't exist 100 years ago. Football was a working class pastime 100 years ago, but now it's practically the national religion. The NHS is probably the most agreed on political issue in the UK, but it didn't exist 100 years ago.
The religious values that Britain adhered to in the past have been gradually taken over by secular humanist values, having begot most of them in the first place. What used to be called Christian values are now secular British values, divorced from their religious roots. In a way, ye olde England has replaced the Garden of Eden as the paradise that believers fix their sights on.
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