A few years ago, Dave bought me an “easy Sudoku” book for my birthday, and it pretty much took me until my next birthday to work my way through it. So it was time, stealing this challenge from Sam, to up my game and move on to the next level. I trawled through the Guardian archive of puzzles and, rather than making a completely random choice, I spotted that they had a medium level Sudoku on my birthday this year, so that’s the one I picked. It had a rather nice symmetry to it too. It took me about half an hour to complete. I could actually feel my brain hurting all the way through.