It looks like an Ephgrave but the 3-digit frame number doesn't tally. probably small builder, and custom made for someone because of the long top tube. Argos resprayed it and put their own decals on it when we couldn't find out what it was.
The fork wasn't original (it came with a 26TPI Raleigh chromed job) and Argos made this matching one with the vintage-style tight bend. I'm afraid I insisted on a plain steerer though, because I had too many problems with the quill stem.
Components are a mixed bag but the hub is a Sturmey-Archer AM, probably the nicest gear-changing apparatus ever manufactured. I have four of these hubs in varying states of wear, from NOS (!) to utterly worn smooth and rather rattly on rough roads - but they all work just the same. I even use one on the Brompton. The single low-rider boss, by the way, is for a lamp.
I don't suppose anyone has NOS white Bluemels mudguards for sale?