Help with an endgame position

White to play and win.

Whats the trick here?

Start with Qe1 and keep pressure until the bishop has to move and leave the pawn undefended. Then take the bishop or find a fork to capture black pawn and finally promote your pawn

Hi Mathias, thank for the reply. My problem is that I dont understand why black should ever move the bishop, he could simply keep moving the king.

the goal for white is to win, not draw. if you for example get the black king on a4, queen on b6, you can force a bishop move. to get there, build a cage for the king & make it ever smaller. very difficult, but possible.

played it through. bit messy, but it illustrates the concept well I think.

Or again:

Wow guys, thanks a lot. Now is completely clear, if the king has no legal moves the bishop has to move. Seems obvious now 😀