I remember seeing on a concord undergoing base maintenance at Heathrow, a series of strong-point mounts on various frames along the fuselage, whilst she was de-panneled. I was told by one of the senior engineers there at the time that they were a modification to the original design spec, insisted upon by the then-current government as a condition of the financial assistance given to the project during it's "floundering" period. Their purpose, it was assured, was for the attachment of either a form of bomb-bay structure or external stores carriers. Whether either were ever developed is something I have never managed to find out.