do a Devon Loch

To achieve a sudden and unexpected failure or loss at the last minute, especially in sports. (Devon Loch was a horse poised to win the 1956 Grand National when he suddenly leapt and fell, ultimately losing the race.) They were up by three goals, but then they did a Devon Loch in the last few minutes of the match. Now that they've done a Devon Loch on their first attempt to secure the championship, I definitely think we've got the psychological edge. There's always the chance we could do a Devon Loch, so, to me, no lead is safe until the clock expires.