[Antrax]

Matchpoints, diagram is accurate.

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Lead: 5♣
The trump situation is

Spoiler

N started with Axx

If it's relevant, S is a world class player, N is his sponsor.

Your line?

[Antrax]

Is this too difficult or too easy? Most tables made 4

[FrancesHinden]

You need to avoid losing a heart, a spade and two diamonds. There is very little you can do in the way of a useful endplay, so it's possible you will end up needing to decide which two diamond honours North has got.
In any case, I would win the club in hand and play on trumps.

I am not going to cash the second club before playing on trumps, because I don't want North to switch to a diamond when he wins the ace of hearts. I want to leave him with a club exit.

North will take the ace of trumps and play something back - what is this?
Suppose it is a club. Which one? (i.e. are clubs 7-2, 6-3 or 5-4?)

I would win this in dummy and take a spade finesse.
What happens?
If it loses and a diamond is returned, then South probably has the ace (because North has turned up with the SK and the HA and passed in first seat), and hence I need North to have the Q10.

If the spade finesse wins, I draw the last trump. When South has the singleton trump I have a choice of lines:
(i) ace of spades and another spade, gaining when South has Kx of spades.
(ii) play a diamond. I can't think of a layout where this gains over simply cashing the spade and seeing what happens, although it does give North the chance the misdefend.

[Antrax]

Thanks a lot Frances. This:

Quote

If it loses and a diamond is returned, then South probably has the ace (because North has turned up with the SK and the HA and passed in first seat), and hence I need North to have the Q10.

was what my partner missed at the table. Not that S has the ace, that much he knew by playing the way you suggested (N indeed returned a club when in with the ace of trumps). But that if he has any hope of making, N must have the T as well as the Q, so he should run the 8♦ when tackling diamonds.