The war Mr Hussein launched in 1980 to bleed the Iranian revolution, an upheaval that had rattled his secular regime by creating the first-ever Shia theocracy, cost 1m lives.

ECONOMIST: Shia Islam

In Egypt and Syria, where secular despots gave Christianity a shield of sorts, political upheaval and Muslim zeal threaten ancient Christian groups.

ECONOMIST: Religious freedom

Terry Sanderson, president of the National Secular Society, says the fall in the number of Christians showed a "huge upheaval" in attitudes towards religion.

BBC: 2011 Census: Changing lifestyles in England and Wales