This is a genuine request for help in identifying this bike. It's steel, most likely the 531 as stated on the decals (it is 'pingy' steel and appears to be butted) and it is almost certainly British. What's not sure is the framebuilder....is it a vintage Overbury's, a very old Saracen or is it something a little more esoteric and bespoke?

It belongs to a fellow RetroBiker and is a very fine build indeed, check out the circa 1980 M700 Shimano Deer Head, the amazing Nitto stem and the H-U-G-E amount of space behind the seat tube

If you can positively ID this bike then contact me via Goatsurfer.com or via RetroBike