Chess Puzzle - Week 3

This week's puzzle is a position from a game by our own Peter Gibbs; his match against Boris Spassky in the 1960 Student Team Championship :




Spassky - Gibbs, Leningrad 1960
White to play and win

I found this puzzle quite difficult - I would be interested to know if the first team players thought so too. For the rest of us, here is a hint. At first glance, it looks as if Peter is doing okay against the future world champion, however, looking closer, you can see that one of his pieces is vulnerable - how did Boris expose this weakness so clearly that Peter resigned?

Full marks for initiative, but no bananas if you ask Peter for the answer (or Boris Vasiliyevich for that matter). Solution next week.

Solution to last week's puzzle: 1. Qxh4! Kxh4 2. Rh7+ Kg5 3. h4 mate.