I think it is a variety of Eryngium but I can't remember
which one, sorry.

Cerinthe major Purpurascens (Honeywort).

Thank you

Hi, it is a Cerinthe, but C major is an annual, sometimes biennial, C glabra is a perennial, but the flowers are yellow, so not that, Derek.

I would have agreed with Shirley tulip but I did think it was a self seeding annual. I checked on the following website and am now totally confused. It says it is a perennial which dies down in winter and then it goes on to describe it further down the page as an annual.
https://www.rhsplants.co.uk/plants/_/cerinthe-major-purpurascens/classid.2000017162/
It looks like it has self seeded on to the gravel path. I remember it in Spitzhenrys garden where she described it as self seeding readily. She does not seem to be around so we cannot ask her.

Hi Scotsgran, it can be a bit confusing when annual plants start seeding themselves about, they disappear in winter the sameas herbaceous perennials, and then they reappear the next year, giving the impression that they're perennial, Derek.

This plant appears in my garden every so often, some years not at all, others quite prolific!

I knew that Derek but have you checked the link I looked at. It is totally confusing and that is an RHS website. On other websites it does say annual, biennial or half hardy perennial. Just in case you cannot access the link I have copied the heading
"Buy honeywort Cerinthe major 'Purpurascens' - rhsplants.co.uk
https://www.rhsplants.co.uk/plants/_/cerinthe-major-purpurascens/classid.2000017162

This perennial dies back to below ground level each year in autumn, then fresh new growth appears again in spring. Position: full sun or partial shade" and another link says this "Buy honeywort Cerinthe major Purpurascens - rhsplants.co.uk
https://www.rhsplants.co.uk/plants/_/cerinthe-major-purpurascens/classid.2000014757

Buy honeywort Cerinthe major Purpurascens ... A striking and versatile evergreen plant, in milder areas it will carry on from year to year, but should generally be treated as an annual. Ideal for adding interest to the herbaceous border. Before using in fresh arrangements, dip the ends of the stems in boiling water for thirty seconds. …"
I think that clears up the mystery. It is definitely talking about C.major Purpurascens.

Hi Scotsgran, yes I see what you mean, very confusing, but I've always known it as an annual, from my apprentice days 56 years ago, so I'll stick to that😊😊😊, Derek.

Derek depending on where Kentishman lives (Kent?) it is possible that milder weather means the plant can be a perennial. Apart from that the question added to my knowledge of how to treat the flowering stems before using them in an arrangement. I hope we have been of some help Kman and thank you for asking the question. This website fairly expands one's interest in plants we may never have heard of before joining.