1NT was announced as 15-17
2♦ was alerted and explained on asking as both majors
2NT was a natural raise
The doubles were for penalties. The first one should have been alerted, but very few players can get the hang of this, and I expect all the players round the table assumed the doubles were for penalties.
Before her final pass, South hesitated and said "perhaps he's showing only diamonds" and passed. West, who recently completed the EBU club TD course, called me and asked whether South had to act as though North is making a forward-going move agreeing spades, i.e. whether she was allowed to pass.
I checked with the convention card that the explanation was correct (North admitted he had misbid), and I said that I couldn't express an opinion on their choices of action at this point, but I told them all that any alerts, explanations and comments by North and South constitute unauthorized information which they must take care to avoid using to their advantage. EW should call me back at the end of play if they suspected that NS may have used such information.
Result: 4♦X(N)-2, NS-300.
West called me back and still wanted to know if South was allowed to pass. What do you think?