Today's position comes from the wilder fringes. Composed by Kjell Widlert and Bo Lindgren in 1978 it is a "series help-mate in nine" which means that Black must play nine consecutive moves to reach a position in which White can deliver mate in one.

As with many problems in a "Fairy Chess" genre, the justification of altering the rules of the game comes in setting a pretty idea that could not be accomplished within the normal rules. Try solving this one, then see if you think the bizarre rules were worth while.

First we must look for likely mating moves by White. A pawn move is unlikely: dxe4, d4 or dxc4 could all just conceivably be mate, but Black will never get all his pieces on the right squares to collaborate in a mere nine moves.

Bh3 or Bg2 could also be mate, but again it needs more help than Black can provide in the time. The most likely - and correct - idea is for Black to capture on d3 and contrive to allow Bxb5 mate at the end.

He'll need to hide his queen somewhere to prevent it interposing and he'll need to clog up the f8 and d8 squares to ensure that Bxb5 is mate. Since Black is not allowed to deliver check in his sequence of moves, there's also a problem about what captures on d3. Now look at the answer and see how it all fits: 1.0-0-0!, 2.Rxd3, 3.Qd8, 4.Qf8, 5.Kd8!, 6.Ke8, 7.Rd8, 8.Ra8, 9.Bd8 and now Bxb5 is mate. An elegant demonstration of castling and un-castling.