Some of my friends have an annoying habit. They phone and ask if I can do them an absolutely enormous favour. Then the favour turns out to be tiny: looking after little Johnny for an hour on Saturday or picking up some dry-cleaning.

Politicians have a similarly annoying habit. They claim to have big plans for reforming the tax or welfare system. Then it turns out that all they intend to do is lift the threshold for inheritance tax or tighten the qualifications for a sickness benefit.