“In this world nothing can be said to be certain, except death and taxes,” wrote Benjamin Franklin in an oft-quoted letter of 1789. It is a good line, but he missed one thing out. “Death, taxes, and dispiriting religion statistics from the British Social Attitudes survey” may not quite have the same ring to it. But as any sociologist of religion or church professional of the past 35 years could tell you, they come around as regularly as a ­lacklustre sermon on Trinity Sunday.