A date for your TV diary: next Tuesday, the 31st of March 2009, at 9pm, BBC2 will screen the Horizon programme Alan and Marcus go forth and multiply, in which actor and comedian Alan Davies explores his fear of maths with mathematician and author Marcus du Sautoy. Together they will visit the fourth dimension, cross the universe and explore infinity, and along the way Alan does battle with some of the toughest maths questions of our age. Let's hope he's done some swotting with Plus first!