When (if) the world returns to normal and live bridge tournaments resume, there are two things I will miss after all these months of virtual everything: playing in my onesie and the UNDO button.

The UNDO button does what it says on the packet. If you ‘misclick’ you press it and you can correct your bid or play, if your opponents agree. Obv you have to do it quickly and it is technically only for clear mechanical errors (for instance you intend to press Pass but accidentally hit 7nt). Occasionally I have wondered whether players were using it as soon as they realised they had made a mistake. You can reject the request for an undo, but in practice that rarely happens. And even more occasionally, allowing an UNDO is the only way to make your contract (see diagram).

South’s hand looked like a strong NT to him, and who can argue? Six-card suits are catnip to most bridge players. West started with the ♣5 to the Queen and Ace.

Declarer obviously has no problems if the Diamonds are running but if they aren’t, he may not have an entry to hand. If only he could make the defence win the Jack of Diamonds on the first round of the suit — then he would have eight on top and no problem establishing a ninth somewhere.

Consequently, at trick two, South made the very intelligent play of a small Diamond to the nine in dummy. This was clearly not expected by East, who followed small, but two seconds later he hit the UNDO button. East was allowed to change his card and hurriedly collected the trick with the Jack!

I wonder if he ever realised he had let through the contract by changing his mind?