We sat at EW. Optimum contract was NS 4♥ which the opponents were the only pair who could bid it. 5 out of 7 tables ended up at 1NTW-3 or 1NTW-4 which meant -300 or -400, but we got -620 because they made 4♥ which was a bottom.
Was this disaster caused by using a strong NT instead of weak NT? (It is the UK which I suppose weak NT is the norm.)
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Opponents were lucky. 4♥ is a poor contract.