I have a little puzzle for everyone.
The flowers can best be described as being similar to the houseplant
known as the shrimp plant. The red-purple bracts are four-sided, with
smallish purple flowers. I wish I'd picked one off the main bush and
pressed it, for I'm working entirely from memory here.

The leaves are heart-shaped. The original is a fast-growing metre+
high bush which seeds freely and loves alkaline soil (it was in
Weymouth).


Google doesn't turn up anything for purple shrimp bush :-)

A little late in answering but it might be Cerinthe major
purpurescens.