Quartic

West at my table seemed fairly inexperienced. I don't remember what she discarded, so maybe her partner had no clear signal.

♦T - I don't want to give away the 9th trick with an aggressive lead. Though the ♠ is right on some layouts of course.

Which pair(s)?

I wasn't at the table that opened 3NT, but I think they said later it was a sort of gambling 3NT.

Playing in a junior teams match, we bid to 3NT, promptly doubled by East: [hv=pc=n&s=s7ht62dakq742caq7&w=skjt9862hdt95c865&n=sq3hj873dj86ckjt2&e=sa54hakq954d3c943&d=s&v=n&b=15&a=1dp1hp3dp3ndppp]399|300[/hv] East cashed the AKQ♥, but then exited with a ♥, allowing me to claim my 10 top tricks for +950. The bidding at the other table was a little bit more wild. [hv=pc=n&s=s7ht62dakq742caq7&w=skjt9862hdt95c865&n=sq3hj873dj86ckjt2&e=sa54hakq954d3c943&d=s&v=n&b=15&a=3np4np6dp6ndppp]399|300[/hv] West led a ♠, and the defence accurately held South to 3 tricks for -2600.

[hv=pc=n&s=skt82hak8754d5cj4&n=sqj4hqt6dak962c82&d=w&v=b&b=4&a=p1n(12-14)p2d(%21h)p2h3d3hppp]266|200[/hv] Matchpoints, playing Acol with a weak NT. We haven't discussed the meaning of bids over 3!d here.

Partner suggested she was worried about trump quality when she passed 5♠. I think in that case a 4♦ cue bid would have been better than 4NT. Edit: We play our 1NT rebid as 15-18, which helps keep bidding lower for invitational hands, so we don't need 2NT to have a wider range.

I didn't bid 3♣ because I wanted to game force. 3♣ is not forcing, though highly encouraging.

[hv=pc=n&w=skqhq2dkt752ckqt9&e=saj864hkj4dq98c75&d=s&v=e&b=3&a=p1dp1sp2cp2np3nppp]266|200[/hv] You receive the lead of the ♥7.

[hv=pc=n&w=sq8742haqj63dajct&e=skj9h94dk7cakqj84&d=n&v=b&b=13&a=p1cp1sp2np3hp3sp4np5hp5sppp]266|200[/hv] We play Acol, so 1♣ showed at least 4. 2NT was 19 points balanced, game forcing. 4NT was RKCB for ♠.