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

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 in one hand and roughly as powerful, though one card shorter, 6-card suit the other and in that hand and a moderately strong 5-card suit and sacre bleu the fourth suit is stopped with the ace! 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. And now where would you like to be? No, not in clubs, though I'd prefer it to spades in a grand slam. No trump!
If we give South the K of clubs for the Q of spades, it would appear that grand slam makes on guessing the doubleton queen of spades. Would you like that? Are you sure you'd go for the drop? Or 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. I might have put this under Preference. Well, South did offer two suits, and with equal numbers, North should go to the first bid suit, not to mention the major over the minor.
Of course a stiff queen opposite an opening diamond bid 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. Of course, going from one suit at the one level to the other at the 7 level gets the two offers as far apart as is possible, but that is neither here nor there.
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 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?
But I think South, who is evidently counting on the A of hearts for his grand slam, would have done well to give serious consideration to no trump. Between his powerful spades and pretty good clubs and his partner's apparently powerful diamonds, surely something should jell for 12 tricks outside of hearts. Hindsight? I'll let you be the judge.