This week it's the maths of puzzles, and how to get wrap your brain around the fact that the answer isn't obvious. Rob Eastaway is my guest- the first returning guest. He has a book out called Headscratchers - a compendium of puzzles from the last five years of the New Scientist. And he's over in Ireland for Mathsweek. (check out mathsweek.ie). And given the weekend that was in it, we really have to do a snippet on the maths of rugby.