Lysichiton americanus

i'm sure it suffers worse weather in its native habitat

Probably, Andrew - its roots must be firmly in the bank, though, as the stream was a raging torrent and I thought it might have been washed away!

That reminds me I should go up to Harlow Carr and see them. they have a lovely display.
Glad yours survived.

It's growing bigger every year! Not like the ones in the RHS gardens yet, though.

How lucky was that.......making a decent plant though.

To me that plant looks like what we call a skunk cabbage. On an area just outside the village there is a large area full of them. Impressive.
Clementine

Yes, that's its common name, Clementine. They like damp places.