"Mad Cow" wrote
Thanks Bob and Garrapata.

I suppose the taxonomists are right to separate these species!
Apparently they have the splendid common name of Dogstrangling Vine.
I'll write that on a label and take care not to let it seed.

It's growing out of a clump of Solomon's Seal that I bought a few years
ago from a voluntary body's plant stand. Maybe it's establishing itself
as a garden weed here but unless it can grow during our mild dark
winters it won't succeed in uncultivated places.

Might be worth asking the RHS if it's becoming a problem, I think you can
e-mail their "garden help" people.
http://www.rhs.org.uk/About-Us/Contact-us

--
Regards
Bob Hobden
W.of London. UK