In the life of a central banker, having to write an explanatory letter to the chancellor - as Mervyn King did this week - is about as tough as it gets, the equivalent of a naughty schoolboy having to explain why his homework is late.

But it is also a reminder that inflation is far from a slain beast. The consumer price index now stands at 3.1 per cent. And the more comprehensive measure - the retail price index - which also includes housing costs such as mortgage interest and council tax, stands at 4.8 per cent.