Is this a win?

 

Black to play

The position shown occurred during a CC game that I was an arbiter for. At some point earlier White thought the position was drawn, although I am not sure a draw was ever offered. When this position was reached Black did something that only happens in CC. Instead of playing a move, he claimed a win, which was checked by referencing a 7 piece tablebase. I'm not sure how long this process took (probably seconds!), but the claim was upheld. 

I was a little surprised that this in fact is a win, but after checking it against a 7 piece tablebase I was less surprised by the result, but very surprised about the actual winning method. In fact there are 2 different winning plans (based on how White defends) but both of them are quite ingenious. The first involves getting the Black king to f4 and the rook to e3, and works if the king is on the 2nd or 1st rank. With the king in a 'box', Black forces the king across to a1, and the threat of mate forces White to unprotect the e pawn. Black will capture the pawn and then have an easy win. 

The second (and more amazing) win is if the White king gets up to the 3rd and 4th ranks. The Black puts the rook on e5 and plays Kf4-g6-h6!-g7!-f8!-e7!-d6! before using the same 'box' strategy to force the White king to the edge of the board.

An incredibly clever idea, and one I think would be very difficult to conceive at CC chess, let alone OTB