This Sudoku puzzle published in The Telegraph claims to be the world’s hardest puzzle, though I am not exactly sure how one measures that.
The Everest of numerical games was published by Arto Inkala, a Finnish mathematician, on his website and is specifically designed to be unsolvable to all but the sharpest minds.
On the difficulty scale by which most sudoku grids are graded, with one star signifying the simplist and five stars the hardest, this puzzle would score an eleven, he explained.
Instead of being able to spot where a number goes based solely on the boxes that have already been filled in, most moves will face you with two or more spaces where a number could fit.
Only one of these is correct, but to find it you must examine all possible options for your next move and perhaps the move after that, continuing in the same vein until all but one potential route results in a dead end.
Mr Inkala said the most difficult parts of the grid require you to think ten moves ahead, exploring a series of permutations at each stage in order to eliminate all routes other than the right one.
All I can say is that it looks really tough and completely defeated me. It is clearly not to be attempted by the faint-hearted.