This was perhaps the most exciting hand from the European Champions' Cup Final between Parioli Rome, Italy, and Schaltz, Denmark. It's from the final segment where the Italians were ahead by miles. However, the bridge was absolutely great till the end.
As West you have arrived in 3NT after an artificial auction where East has shown 17-19 hcp with 5+ hearts, either balanced or unbalanced. You have told everyone about 6-9 hcp, not 4 spades, no 5-5 or 6-4 shape, and no 7-card suit.
Your LHO is Fulvio Fantoni. After some consideration he leads ♦4. Plan the play please. It may not be as easy as it looks.
Roland

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West: 3NT
Lead: D4