The problem is ‘helpmate in 3.5 moves’. As you may know, in a helpmate we have a sequence of black and white legal moves in which Black and White conspire together to produce a position in which Black is mated. Just in order to be sound it has to be the case that it looks very unlikely that White could mate Black and that is certainly the case here! In a helpmate in 3 we’d have Black kicking off a sequence of moves leading to mate but as this is in 3.5 move we actually start with White – so we have WBWBWBW sequences. “Sequences” plural, because there is a second part: (b)Pc4>e4 – when that pawn is shifted the (a) solution no longer works but a new solution now does.
You may like to consider how on earth White could mate Black here. Or you may prefer just to read on. (Or that other option – switching to another BCT article – remains open, of course.)
The white rook is so immobilized that it looks as though it will have to be the white bishop that does the legwork. It seems that there’s a real risk that when the white bishop moves Black will have no option but to capture the white rook or even administer mate himself. The only alternative after a move by the white bishop is to interpose one of the black Knights, but these give check. There may be a possibility then, though, of playing PxN, and it might be a good thing to get White’s one other combatant, the c2P, involved in the action in this way…
Even so, the only way in which the white rook is going to be able to participate in giving mate is if the mate is by double check…
Putting this all together, you might (or may already have; if so, well done!) come to the first solution (confusingly, because in most helpmates Black begins problemists always write helpmate solutions as though Black had started the game): 1…Bxg6+ 2.Ncd3+ cxd3 3.Ne4 Bf5 4.Rhc6 dxe4. And similar ideas work in (b) 1…Bxb5+ 2.Nfd3+ Bxd3 3.Nb3 cxb3 4.Qc6 Bc4. Move by move the solutions show the same strategy (or should I say “strategems”?!), but the details are all different, which really is a prerequisite for a problem like this, and one reason why the tourney judge gratifyingly had such a favourable impression of it.
Christopher holds the Grandmaster title for Chess Problem Composition and uses his skills to write a regular column for the Bristol Chess Times. He is also a longterm Horfield Chess Club player (where he is acting secretary).