Tim Krabbe gives this position on his list of serious promotions to rook and bishop:
[FEN "8/8/5b2/8/K7/4N3/kp6/8 w - - 0 1"] [White "Boniface"] [Black "Pugh"] [Site "Bristol"] [Date "1995"] 1. Nd1 b1=B
And states that: "Although the position was then technically won for Black, he did not manage to win, and a draw was agreed at move 92."
Can black win the resulting 2 bishops vs knight ending, and if so can it be done within 50 moves to avoid a draw? I had Stockfish 5 grind at it for almost two hours and a depth of 83 but it couldn't find a win.