Thank you all for your replies, and particularly mikeh for the very detailed analysis.
The full hand was:
I played two rounds each of the black suits, and then led up to
♥J, losing to E's
♥Q. E then returned
♥7; I didn't finesse (I thought the
♠s were 3(W)-4, as they were, and I was pretty sure that
♣ were 3-2, which I didn't think gave me any indication of how the 7-7 red cards were split) and when
♥10 didn't fall by the third round I went down.
As the cards lie, it seems that this defence kills the red-suit squeeze, and with it the contract, whenever the
♥ is played up, so though my timing probably wasn't optimal it wasn't crucial.
The hand was played in slam at 6 tables out of 15 (the other 9 were in 3NT), with four making, two after the
♥2 lead to
♥J and E's
♥Q: one of those declarers played up to
♦Q and the other made when W discarded a
♥ on the last
♣.
The other two successful declarers had
♠8 as the opening lead; one led up to
♥J, and made on the squeeze when E returned a
♦ and declarer went up with
♦A; the other played
♥J from dummy, and, after E covered, later played up to
♦Q.
The other declarer to go down also had the
♠9 lead, and also led up to
♥J, but by then had already played
♠A & K and all the
♣, leaving the bare
♦A in hand: E was then able to exit with a
♠ to dummy's Q, allowing W to discard
♦K and keep the
♥.