If Ever there was a Hand. . .

Q 5
A 9
A K J 10 9 8 6
5 3
8 4 10 9 2
7 4 3 2 K J 10 8 6 5
7 3 2 5 4
K 9 8 6 7 2
A K J 7 6 3
Q
Q Opening Lead: 2 of hearts
A Q J 10 4 Vul: E-W

WestNorthEastSouth
Pass 1 Pass 1
Pass 3 Pass 4
Pass 4 Dbl 4 NT
Pass 5 Pass 7 All pass
If ever there was a slam hand that called for no trump, this was surely it. There's a powerful 7-card suit and roughly as powerful, though one card shorter, 6-card suit and a moderately strong 5-card suit. No trump lets you free to exploit the suit that works. You can't know ahead of time how solid a partner's holding is. Let's trade the Q of spades for the K of clubs. We wouldn't expect the bidding to be any different. Now a spade grand slam doesn't look quite so appealing, after all, does it? Are you sure you'd go for the drop? Wouldn't you feel just a little safer in no trump, running diamonds and clubs for 12 tricks with a heart and two spades to go?
So why do I put this under Preference? Well, South did offer two suits. Of course a stiff queen opposite an opening diamond with a jump rebid should give partner some vector toward counting on that suit in no trump, if you have all the aces. But he didn't, and it is still incumbent upon North to show preference when his partner dismisses diamonds and bids a second suit. And that means that with an equal number in the two suits, he must pick the first named (especially since it's a major and the other a minor). He absolutely must. Of course, going from the first suit at the one level to a call for preference at the 7 level gets the two offers as far apart as is possible! Did North forget his duties during the time lapse?
As for the bidding, I can't be certain what the 5 club response to 4 no trump was. My hunch, the only explanation that makes sense, was that they were playing Roman Key Card, and North was counting on diamonds to be trump, and thus counted the K of diamonds as an ace, and playing 0 or 3 aces calling for 5 clubs, bid accordingly. But I'm not sure. In any event, the meagre doubleton in clubs compared to the Q doubleton in the first bid (major) suit makes the preference call of 7 spades unambiguous, and in the IMP game would have brought a score rather close to that of the 7 no trumpers. I have a notation saying that the swing was 22 IMP's. Expensive for not paying attention, no?