Chess Puzzle of the Week (96): Solution

Last week I left you with this endgame study by Richard Guy.

It could also, I suppose, have been presented as a mate in 10.

It solves like this:

1. Nf2+ Kg1 2. Nh3+ Kh1 3. Ka6 Ne1 4. Be4+ Ng2 5. Kb5 (Ka5 takes a move longer) 5… a5 6. Kc4 a4 7. Kd3 a3 8. Ke2 a2 9. Kf2 a1=Q 10. Bxg2#

Congratulations if you solved it.