My Saturday afternoon involved sitting in a hall in Ilkley watching children play musical chairs to demonstrate the population dynamics of lemmings. It’s not often that one can write that. As you can probably tell by the picture, I was at Marcus du Sautoy’s talk at the 2010 Ilkley Literature Festival. The King’s Hall is one of Ilkley’s larger venues for the festival. Outside hangs a large banner for the Complementary Medicine Festival and an advert for a gig by Dr Feelgood (that’s rather fitting said my good friend Paul when we were in Ilkley last week for a different talk). However, Saturday was a mini Maths Day in Ilkley with Rob Eastaway giving two distinct talks at the Playhouse and Marcus du Sautoy giving his at the King’s Hall. The talk, titled The Num8er My5teries, was billed for ages 0-100 and there was indeed a wide spread of ages filling the hall to capacity (about 500). Young people were well represented. The local science communicator Marty Jopson did the introductions — and sneaked in a plug for the Otley Science Festival (16-20 November in case you are interested). The first half of the talk was about primes. Marcus began with a discussion of why David Beckham chose the prime number 23 as his shirt number when he joined Real Madrid. (I’m sure that there’s a good mathematical joke about Complex Madrid but I still haven’t come up with one yet. If you can think of one, email me.) Marcus was aptly dressed in a purple football T-shirt with an equation on the front and with Galilei and a 17 on the back. I’d never seen him give a talk like this before and the first thing I noted is that he talks faster...