Warning: this post will mean nothing to you unless you live or have lived in London. It may — and this is entirely the point — still mean nothing to you even if you do!
It boggles me how many people — including, apparently, professional sign-writers — still think that London is divided into two telephone codes: 0207 and 0208. Having lived through the 01/081/0181/020 debacle, I entirely understand where the misunderstanding comes from. But it’s been nearly ten years. And there are otherwise intelligent people of my acquaintance who refuse to accept my explanation that all London numbers are eight digits long and have the exchange 020.