The deal is taken from a hand taken from a beginner's class in Norwich, which was reproduced and given to me as declarer. It was setup so that if declarer gets it right they always make it. It ought to have been easy - but I bodged it.
I was South. We quickly got to 4♠ and after some thought, West lead a Diamond. There are clearly ten tricks (five trumps, three Hearts, two Diamonds), it's just a case of taking them all.
The whole point of the hand, I realised afterwards, is to be wary of the singleton Diamond and draw trumps before playing Diamonds. To do this, while also getting the two Heart ruffs, you have to return to hand after each ruff with a trump. So, after winning the initial Heart in hand, the sequence might be: ♥A, Heart ruff, trump back to hand, Heart ruff, trump back to hand, draw trumps and claim.
I didn't do that though. After the first Heart ruff I drew two rounds of trumps, ending in hand, and lead up to the ♦K. So I have been a bit careful, and was hoping the person with a singleton Diamond was out of trumps. He wasn't, but because I was leading up to the ♦K (rather than cashing it) I still had ten winners available if they couldn't take three Clubs, which indeed they couldn't.
So I made 4♠=, but missed the point of the hand. The notes said "remember, trumps can be used as transport between the hands too." It's a tough game.