Plant Identification

[Zeuhl]

Hi, can anyone identify this plant?
Found yesterday, growing profusely next to roadside drainage ditches in and around the village of Chidham, West Sussex.
Mrs Zeuhl can't find it in any of her books and it is beginning to annoy her - which is beginning to annoy me. Help!

https://zeuhl.smugmug.com/My-First-Gallery/i-zKhd3mP/A

[Chipchopper]

Yes butterbur well early!

[Zeuhl]

Indeed. Assuming they ever stopped flowering.
Lots of insects yesterday (flies end of December!) and a couple of water voles out and about. Let's hope a cold snap doesn't kill them all off.
Thanks again x

[Chipchopper]

Interestingly, the plants name has derived from the fact that its leaves were once used for wrapping up blocks of butter.