How tall is it? The flowers look like C. dealbata...but I can't be sure.

A close up of the leaves and flowers would make life easier. There are a fair number of Centaureas around. I would say that the leaves look like C. triumfettii, but that is pure guess work.

Centaurea pulcherrima ?

I'm with Hywel Centaurea pulcherrima

Thanks again, Hywel and Pimpernel. I reckon that is 3 out of 3. Off now to have a large slice of humble pie. I will enjoy while renaming my photos of Cornwall.