Dealer W, E/W Vul.

The bidding is passed round to South, who must have been thinking of 6D once he had sorted his cards.
The bidding goes:
2C 2D 3D 3S 4D 4S 6S
South realises that his hand is going to be dummy in either contract and correctly choses the better slam.
He was worried about entries to the North hand to cash long Spades if Ds are trumps.
Sitting East, I lead my singleton D hoping for a ruff and one other side suit winner.
A H or C lead would defeat the contract - was that a clear error??
After AD, needing to get back to hand after cashing AS/KS, declarer tries the KD. I ruff and now lead a C to promote a trick for West.
Too late!  Declarer can win his Ace and ruff a D high, draw trumps and get back to dummy with AH to cash long Ds.

At the other three tables N/S bid and made 5D, and went one or two off in a slam.  All negative results for our team.
None the less we managed a small 9 IMP win over a strong Malton team.

PS.  The hand was played by all teams in Division 2 of the League, that is at a total of 16 tables, with very mixed results:
3 bid and made 6S, 7 were defeated in 6S/6D and another 6 played in a game.  (At one table North opened a weak 2S, South bid 6S)