Hi Pauline
I have sent an email to the Dundee Botanic Gardens for an answer to your question.
Hopefully they will reply to my mail, then in turn I will let you know.....Tg
Thank you Tee Gee; it really is very kind of you to do that.
Obelixx, I have just looked at verbascums on Google so thank you for your suggestion. I came across Verbascum thapsus - great mullein and it looks similar apart from the fact that those in Tee Gees photos appear to have green, glossy leaves rather than silvery ones. Definitely a verbascum though.
It's making sense now as my OH said that we have them in the garden and he is continuously pulling them out as they are weeds. They only grow to a foot or two so are nowhere near as big as those shown in the photo. Ours have silver, hairy, felt-like leaves and a yellow flower.
Thank you for your reply, Palustris. It will be interesting to see if Tee Gee gets a reply from the Botanical Gardens. A lot of the verbascums look very similar.