This plant, native of Europe, naturalised in UK, but rare, is in Colden Dale. I stumbled upon it today. It is a bit smaller than the common butterbur, but quite spectacular. There are many flowers up now, in a spot well off the usual footpaths.
Frank Murgatroyd in his Flora of the Halifax Parish (1995) has it only in a wood near the Ainleys, Elland, and Bullace Trees Wood, Sowerby. The West Yorkshire Plant Atlas only mentions a site near Storthes Hall, Huddersfield.
If any plant enthusiasts want to see it, I can probably arrange time next weekend to lead an
impromtu HSS walk up to see it, (about 1 hour easy walking,) while it is in flower.
Eight very fresh clumps of frogspawn in one of the silted-up dams there today.