This seems like an easy set of hands to reach grand, but not so much at the World Championships.
The first question is Responder's selection of a path. I dislike the splinter option with a fifth spade, poor spade honors, and slow values. I also dislike Jacoby 2NT, which I hate generally anyway. So, 2D seems rather obvious.
This yields an ugly-sounding 3C to Responder, although that could be predicted. What else but 3S?
Opener bids the obvious 3NT, so Responder shows his good diamonds -- 4D -- two of the top three. Opener likes that, but 4H ass LTTC seems obvious, lacking the heart control.
Responder has the heart Ace, which cannot be bad. sure, the stiff in clubs does not help Opener's club suit, but Opener knows that Responder lacks any honors and is till interested, and the stiff with five trumps seems nice. Seems like Responder has the best information, and no good way to show the fifth spades, so 4NT seems right.
Opener shows four. Wow. The Queen is not needed, but outside cards might be. Sounds like 5NT.
This is really cool. Recall that Responder already cuebid 4D, showing two of the top three diamonds. If Responder is now seeking a grand, we both know that Opener has the diamond Ace. So, all three top diamond honors are accounted for. This allows Opener to make a really nice call. He bypasses 5C because he does not have the club King. As he cannot have the diamond King or Queen, and is already known to have the diamond Ace, 6D shows the only thing left -- the diamond Jack!
You might think that Opener could just bid the grand, because Responder's 5NT call pretty much disclosed the fifth trump when Opener is looking at the Jack, but Opener does not know about the club stiff. Plus, why not describe your hand perfectly when you can?
Responder never knows about the spade Queen, but the 13th trick seems obvious now that the diamonds are known to run.
Back up if you don't like not asking for the Queen. Responder could do that also, bidding 5H (if regular RKCB) or 5D (if 1430). Opener will show the Queen and NOW can deny the club King but show the diamond Jack.
Back way up, though. after the 2D call, North held x-Jxxxx-KQxxxx-x, white on red. This might get messier. Not sure if that was the problem sometimes, but not always. The 2D start still works whenever Responder can bid 3S at his next turn. And, that was in fact available sometimes.