Since... 1994!

Black has just made a very unfortunate move...

that has cost him the game. What is the move and how does white mate in one?

Submitted by Thomas McKane

(White: Ke1, Rc1, Rc8, Ba3, Bg4, e4 ,f5 Black: Kd7, Rf7, Rd4, Bb5, Bb6, e5, f6)

Solution