Imagine waking from a 50-year coma to find that the TV in your recovery room was permanently tuned to a station playing classic British detective drama. You’d pretty soon come to the conclusion that the most dangerous places to live in the UK are not the slums of its larger northern cities but the ivied cloisters of its older university towns, the leafy lanes of Yorkshire farming communities and the half-timbered high streets of Cotswold villages.