It was a mystery that I had not been able to unravel for decades. Way back in 1990s I had found the following position in a wonderful book, Chess Wizardy, ABC of Chess Problems (Batsford.1996) by John Rice. The author happened to mention the following position from a game, Keres-Bronstein, Zürich 1965. But I had a problem. Keres and Bronstein did not play each other in any tournament in 1965. Did this position ever arise in a real game and who played it?
The mystery was finally resolved when I saw Hans Ree’s review of Richard Forster’s book, The Zürich Chess Club, 1809–2009 (McFarland.2011) in New in Chess Magazine (7/2009).
In 1965 Keres and Bronstein had finished a simul tour in Zürich and were treated to a farewell dinner at the home of Alois Nagler, President of the Zürich Chess Club. After dinner they obliged their genial host with a friendly blitz game (5 seconds per move). This position led to the finale of the game.
Black to move
(Time limit: 5 seconds per move)
Note: thanks to those who noticed, we have corrected the diagram