I really enjoyed it as well it was nice to talk botany all day

Having looked at the plant again I agree with you about it being rubrum as it’s not showing any signs of a cordate base to the leaves.

It could be but it is quite stunted it was raining heavily when I noticed it may go back and have another look. I found what looks like Chenopodiastrum hybridum on the sea wall near the car park in Saltburn.