SO WHAT ARE the golden rules for solving these wretched, infuriating, time-wasting, addictive things? What are the secret dodges and strategies that will help you unlock a “fiendish” Su Doku puzzle before it turns you into a gibbering wreck? At some risk to my sanity, to say nothing of my marriage — and with no help whatsoever from Wayne Gould, the inscrutable creator of T2’s daily torture — I have spent a sizeable part of the past three months trying to work out exactly that. I can’t say I now have a foolproof, work- every-time plan. But here are four basic pointers I have found useful.

First, don’t fall into the old “can’t see the wood for the trees” trap. My wife, with (if I may say so) typical female efficiency, insists on writing every possible number into each square. She sometimes copies the whole puzzle on to super-size paper to make this possible. Then she tries gradually to whittle down the possibilities. That works reasonably enough for the easier puzzles. But for the fiendish ones, forget it. All those little numbers simply make your brain spin. You won’t spot the one connection that unlocks the puzzle. Keep as much as you can in your head.

Secondly, don’t get bogged down in one particular square or row that looks so promising that you feel it must be easy to complete. Remember that there are nine rows and nine columns to play with. Keep moving! Thirdly, look for recurring pairs of figures — for instance, the 5 and 6 pattern in the puzzle here. It’s Mr Gould’s amusing way of pointing you in the right direction.

And fourthly, don’t lose heart! I think of a Su Doku as a bike ride. With the easy puzzles, you are freewheeling all the way. They really involve nothing more than mechanical number-elimination. The difficult category tends to be an upward pedal at first, with a fair amount of deduction required. But there comes a point where the whole puzzle falls into place, and it’s downhill from then on.

A fiendish Su Doku, however, never really stops asking you to be deductive and lateral-minded. That can sap your mental stamina, at which point you can easily make a silly error. Better to put the puzzle aside for an hour or two, and return afresh later. Your boss, or your spouse, might appreciate that, too.

Let’s have a look at the fiendish Su Doku which we printed yesterday. Here is the original puzzle, then the three intermediate stages I went through to solve it, and finally the solution. Going from Stage 1 to Stage 2 depended on deducing where the 3s were, from the positions of those helpfully linked pairs of 5s and 6s. The vital step when going from Stage 2 to Stage 3 was to notice another linked pair: the 1s and 3s in the second and third column s. This meant that the first two squares of the first column also had to be 1 and 3.

Then I looked along that top row. It had to contain a 2, but the only place that the 2 could go was either in the fourth or sixth squares. That was crucial, because it meant that in the fifth column the 2 had to be in the seventh square. And after that I found the puzzle started to shed its mysteries like Salome shedding her veils: slowly and tantalisingly at first, but with increasingly exciting results.

Yes, I am obsessed. But if you have read this far, so are you. However, if you find yourself starting to dream of Su Doku squares (as happened to me on Saturday night), it’s probably time to go back to the chess puzzles and the crossword.