Locksmithing and Security

We have just decided that we are no longer accepting jobs from a certain area of Putney in south-west London. There are so many barriers and “no entry”s, that unless you have a specialist map you cannot get to a significant proportion of the residents. And, of course, your customer is necessarily always going to be included in that percentage. And of course that map isn’t available to tradespeople.

I have a brother-in-law who is a topologist—I really do—and he agrees that there are certain streets that you cannot reach, and one street where if you do manage to get to it, you can never leave again. (Topology is the branch of mathematics which says a teacup is the same as a doughnut, which can prove the hairy ball theorem—that you can’t comb down the hairs of a hairy ball without creating a cowlick—and which probably started with the proof, long ago, that there was no promenade that would take a walker over each and every one of the seven bridges of Königsberg just once.)