It is only possible to achieve this in the corner.
This sheet shows you how to get from A to B!
Sometimes when I tell people they need to do this for the BCF I am asked - how often do you ever have to do this?
Well, it doesn't happen that often but the point of learning it isn't just so you can do it quickly in a match.
By practising this in you learn several things:
- using your King to attack in the endgame
- how the two Bishops can work well together
- how to cut off squares from your opponents King.
24.Ke2 The first priority is always to get your King up and working. 24...Kd5 25.Kd3 Ke5 26.Bh3 Kd5 27.Bb2 Kc5 28.Be6
The two Bishops have shut the Black King in half of the board. 28...Kd6 Gaining time by attacking a Bishop. 29.Bg8 Kc5
30.Ke4 [30.Ba3+ is also good here: usually if you give a check you let the Black King out, but here the White King stops it getting to d4.] 30...Kb4 31.Kd4 Kb5 32.Ba3 Ka4 33.Be7 Kb5
34.Be6 White waits with a Bishop move so that the Black King must give way to the White King. 34...Kc6 35.Kc4 Kb6
36.Bd7 The fence made by the two Bishops is moved another step towards the corner. The Black King tries to gain time by chasing the Bishops, but that doesn't last long. 36...Kc7 37.Be8 Kb6
38.Bd8+ Another step. 38...Kb7 39.Kb5 The King can at last advance again. 39...Kc8 40.Ba5 Kb7 41.Bd7 Ka7
One more trick to get force the Black King back. 42.Bc6 Kb8 43.Ka6 Kc8
Nearly there. Another waiting move: 44.Be8 Kb8 45.Bd7 And the King can't retreat. 45...Ka8
Now, this is important. The King is now in the corner and our King is cutting off lots of important squares. So we can arrange mate, being careful neither to allow the Black King to escape nor allow stalemate. 46.Bb4
[46.Bc7 ...is stalemate! So we must move the dark-squared Bishop to this diagonal with check.]
46...Kb8 47.Bd6+ Ka8 48.Bc6#