According to Jenni Russell, my colleague at the Times, David Cameron has lost 13lb since Christmas, mainly by giving up on peanuts and biscuits. Now that’s a lot of peanuts and biscuits. It’s a bit yo-yo, Cameron’s weight, isn’t it? He gets bigger, he gets smaller again, like a giant, very pink, human-shaped balloon that some giant unseen hand is alternately squeezing and relaxing around the legs.