The question I asked Sally was, could North-South have got to slam? Or rather, in the style of most of the letters that are written to Mr Bridge, I asked could my partner have done more?.
As for the bidding, Sally said that South must have slam ambitions to be bidding both minors like that, else he would have signed off in 3NT. So North should recognise that, and having 18 points compared to a minimum of 15, should bid on. She suggested North bid 4♣ over 3♦ (or perhaps 3♠, which I didn't understand). Then the partnership can get to 6♣.
As for the play, Sally said that actually 6♣ isn't a great contract. After the losing Diamond finesse you have three options:
- A Heart finesse (which works, and is what Anna did when playing 3NT+3)
- Drawing two rounds of trumps only then playing Diamonds, hoping the hand with the last trump can't ruff or they are 3-3 (which fails)
- A Heart-Diamond squeeze, hoping that one defender has both four Diamonds and the ♥K (which fails)
Since only one of the three options works, Sally said that actually we were lucky to avoid 6♣!