Well done to Janet and Arnaud who reached 6♣ on 26 points. I wasn't at their table so don't know how they got there but here is how it might be done.

1♥ = Not strong enough for an 8 playing trick opening
2♦  = 10+ points, 4 or more Diamonds,
3♣ = 4 or more Clubs, 16+ points (it's a reverse as it forces North to bid 3♥ to show simple preference for first suit)
4♣ = I like Clubs
4♥ = Cue Bid. I have the ♥ A but am missing the ♦ A as I didn't bid 4♦ 
4♠ = I have the ♠ A
6♣ = That's all I need to know and using Blackwood is pointless as I know partner has at least one Ace and so we will be unable to stop in 5♣ if I use 4NT to ask for Aces

Everyone played this in a Heart part-score but three pairs made nine tricks and one pair made ten, when they should be kept to seven.

East must lead their singleton Diamond

If North plays low from Dummy then West wins and returns the ♦ 3. This is a critical Signal to partner. It is the lowest Diamond West has so it is telling West to play a Club (the lowest suit) once they have ruffed the Diamond. East ruffs and plays a Club as requested. West wins and returns a third Diamond which East also ruffs. That's five tricks to the defence and they still have to take the ♥ A.

If North takes the ♦ A at trick one then West wins any continuation but a Spade and continues the same strategy. East wins the ♠ K if offered and gives West back the lead with anything but a ♠