John lanchester here provides the tin-opener to the money men’s can of worms. The most memorable of his facts (listed in alphabetical order) comes under S for “Seventy-Two”. How long will it take you to double your money by compound interest? Simply divide 72 by the rate of interest. If it’s 6 per cent, it’ll take 12 years. Contrariwise, you can use the magic number to work out how long inflation will take to halve the value of your savings. Hmm, not so consoling.Earlier in the book there is another amusing entry on compound interest. The Indians who sold Manhattan to Peter Minuit in 1626 did so for some beads and trinkets worth, say, US?$26. If those Indians had been in a position to invest the $26 at 8 per cent interest (which Lanchester assures us is by no