MPs. Table result 4♠=. Lead ♥Q
SB, East was apoplectic with rage at this hand from last Tuesday's duplicate at a North London club. RR, South, alerted his partner's 2NT bid and described it as "Jacoby, a FG spade raise with 4 trumps". As he was minimum, he jumped to 4S and this ended the auction. ChCh did volunteer a correction that 2NT was natural before the lead, and the TD was called, but West, Walter the Walrus, still led the ♥Q. He had not responded ("fewer than six points, partner") and North's 2NT was systemically 19-21, shown on the CC as this, so there was MI and possibly UI. South's 4S was not on the CC, but there was an express agreement between Charlie the Chimp, North, and RR that all game bids were to play in all circumstances. SB argued that 4S by South could not be natural, as it was in a suit opened by the opposition. The Rabbit had notched up 10 tricks.
"I think North took advantage of the UI of the admittedly ludicrous explanation by RR of 2NT being Jacoby", he began, "and calls other than pass would have been less successful." "My partner's ♥Q lead, allowing the contract to make, was equally ludicrous, but far from being SEWoG for a player of WW's standard", he continued. "And it might have been affected by the MI".
The TD was far from convinced. "I think it is just rub of the green", he commented. "It is impossible to find peers of RR playing the same methods, so I don't think there are any LAs after this auction." "And I don't think the MI changes the Walrus' lead. He would just lead his top of sequence every day of every week. And he was aware of the MI before he led."
How do you rule?