Nice Puzzle

I'm just half blind when it comes to these kind of moves. took me about 5 minutes to spot the crucial one... it's so obvious after that, you immediately know it's the right one.

Originally posted by philidor position
I was digging my chesstempo problems history and here's one that drove me nuts back in it's time.



[fen]8/p4k2/1p3p2/2qPp1pp/7P/1P2Q3/P4PP1/6K1 w - - 0 42[/fen]
White to play.

small hint: [hidden]I think this is one of those puzzles which some people can see instantly and some will never find the answer. I was in the latter group.[/hidden]

A nice puzzle that I saw in another forum. Apologies to those who have seen it already...