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Thank you all for your help, sorry to be slow in acknowledging, we've been away for a couple of days. Yes, it's a Sambucus Nigra, and in fact it does produce a very few tiny berries, (match-head size) which would argue it's being pollinated? But most of the flower heads simply drop their blooms and that's that, no berries form. Our post lady thinks the soil's too rich for it, hence the very exuberant growth, large leaves etc., too much nitrogen she says.