I knew i missed something obvious Tim, otherwise the move i suggested would already been suggested. But missing a mate in 2 is a bit stupid.

I found it out also myself thinking of the position in the bus home.

Ah i see i wasn't far off with promotion to knight. Missed the promotion to Bishop on g8 though:(

I always like problems with under promotion.

Difficult thing is that Qd5(+) is annoying in almost all the lines. So my guess is you have to start with Kb8 (and after another king move the black king has room to move). Or maybe promote d8/N to keep control of the b7 square. It is hard to calculate everything with all those queen checks black has.

Maybe a stupid question, but why is the line given with Kc2 better for black? I don't see any way to stop the promotion after Bd3+. A king move or rook move, mate isn't possible anymore.

@sergio,

if 1. b6+ Kd1! 2. b7 Kc2 3. bd3+ then 3... Rxd3 4. b8=Q be6+ 5. Ka1 Ra3++

I think this is one another relaxation from afek to the solvers-
very easy puzzle this one is..

1.g8(B) Qb5

(only move - as now white is threatening 2.Bc4# for eg.
1...Qe2 is the only alternative - 2.Be4 Qb5 3.Bf3! +- the queen can't move out of the diagonal as Be2# is threatened.. and white's going to queen)

2. d8(N) +- Qe2 3.e8(Q) Qe8 (3...Qg2+ 4.Qf3+) 4. Bc4+

1-0

Doesn't the fact that 1... Kd1 wins for black invalidate the study? Should it be started at the second move?

Well, we already explained last week, André.

Yes, I now see it too *blush*