Karl Fabel (1905-1975) was a German problem composer who specialised in the weird, the unusual and the very long. The position above is typical of his ingenuity: it is White to play and mate in 41.

The first point to note is that if it were Black's move, then the task would be simple: his only legal move is 1...g3 when 2.fxg3 f2 3.Nc2+! bxc2 4.Nxf2 is followed by White queening his g-pawn and winning well within the specified limit.

So all White has to do is lose a move, but that is not so easy. A knight, always alternating between white and black squares, can never lose a move, and in this position White's king cannot stray from c1 without unbottling Black's monarch from the corner.

White's knight on b4 must come to the rescue, so, with Black's king oscillating between a1 and a2, White brings his knight to a6, c7, e8, f6, h5, g3, f1, d2, b1 and a3. With the black king securely locked in, White now plays his king to d2, e1, f1, g1, then to h2, h1 and g1 to lose a move, then back to f1, e1, d2 and c1. Move 22 to 31 are spent bringing the knight back to b4, finally reaching the diagram with Black to move.

The solution then ends with 31.Nb4! g3 32.fxg3 f2 33.Nc2+ bxc2 34.Nxf2 Ka2 35.Kxc2! after which the g-pawn promotes to a queen at move 40 and 41.Qa8 is mate.

A neat composition with both knight and king making return trips around the board.