A serendipitous joint composition

In constructing a problem, the composer strives to make one thematic solution work – the “intention” – while eliminating all other viable lines or potential cooks. There are rare cases where an unintended solution is discovered and it proves sufficiently interesting to be incorporated as part of the problem. The directmate below illustrates a similar sort of fortuitous situation, in which a twinning device enables the problem’s content to be effectively doubled.

The diagram position was originally published in 2003 by the late Denis Saunders, to show an unusual idea, viz. an en passant key in a three-mover. It’s legal for White to start with 1.dxe6 e.p.!, because Black’s last move could only have been …e7-e5 (see Two problem conventions for an explanation of this type of retro-analysis). Black is released from stalemate and allowed two checks: 1…dxe6+ 2.Kxe4 e5 3.Qc8, and 1…fxe6+ 2.Kg6 e5 3.Rg8.

Fellow Aussie composer Geoff Foster then detected a hidden possibility in the position. By shifting the white king to e8, he creates another mate-in-three problem with a unique key and accurate play throughout. The sacrificial 1.Rg6! now leads to 1…fxg6 2.Qxd7 g5 3.Qg7, and 1…Kxh7 2.Kxf7 Kh8 3.Rxh6. We see two brand new variations, and in keeping with the first solution, White’s queen and rook execute one mate each.