With a little help from my friend Fritz...
1.Ka5
White wants to get the King in front of the pawn in order to evict the Black rook.
1...Ra8+
[ If Black tries to just leave the rook on the b-file, White proceeds with 1...Kd7
2.b6
Kd6
3.Ka6
and the rook will soon be forced out.]
2.Kb6
Rb8+
After all, Black want's to keep the White king out from in front of the pawn. This next maneuver by White is reminiscient of White's winning technique once the Lucena position has been reached and the King is emerging from behind his pawn.
3.Ka6
Ra8+
[ Once again 3...Kd7
is met with 4.b6
Ra8+
5.Kb7
]
4.Kb7
Ra4
The rook has been evicted, and the king is in front of the pawn. White wins.
5.b6
Rb4
[ Black can also try 5...Kd7
but White just continues on about his business with 6.Kb8
etc.]
6.Ka7
Ra4+
7.Kb8
Ra2
8.b7
Kd7
the basic Lucena position. *