None of the contestants in the final of the British Chess Solving Championships found the answer to this problem. Composed by Paul Loschl, it is a helpmate in four moves: Black moves first, and both sides collaborate to reach a position after four moves each in which Black is mated. And there are two distinct solutions to find.

One natural idea (once you have given up trying to solve the impossible task of mating the black king on c2 or d1) is a mating position with the king on g4, a white rook on h4, protected by a bishop on f6, e7 or d8, and a black piece blocking the escape on f3.

The only problems are how to unpin White's rook, and how to get a black man to f3. The answer is achieved with typical helpmate elegance: 1.Rc6 Bh4 2.Rc3 Rh6 3.d2 Bf6 4.Rf3 Rh4 mate. Note how the black rook and white bishop take turns in blocking the long diagonal. Now try to find the second solution. Here's a big clue: the black king is mated on h4.

Still stuck? Well, the idea is to get the bishop to e7 or d8, block g4 with a black man, then play Rh6 mate. Now try again.

Give up? Well the trick is again in the unpinning of the white rook. The answer is 1.Qg8 Bd2 2.Kh4 Bxb4 3.Qg4 Be7 4.Rb2 Rh6 mate!

The starter position for this year's competition will appear in this space tomorrow.