The post that was quoted here has been removedIf white can arrange for black's king to be on a6 when his queen arrives on b8 with black to move then the king can be forced to move down the a-file until the queen can mate. Forcing that arrangement of king and queen is the thing though. Too much beer and not enough sleep for that tonight.
The post that was quoted here has been removedI dont have a beard, but the solution is:
1.Qd5+ Ka7
2.Qb5 Ka8
3.Qa6+ Kb8
4.Qc6 Ka7
5.Qc8 Kb6
6.Qd7 Kc5
7.Qe6 Kb5
8.Qd6 Ka5
9.Qb4+ Ka6
10.Qb8 Ka5
11.Qb7 Ka4
12Qa6#
tell me a better move for black at any time, and I will gladly tell you a better way to mate.