There is quite a bit of info on the net about him, found this which might give some background:
Rory O'Brien had two shops in the East London area, and was a well established lightweight dealer. The main shop was in Romford and had been in business since at least the early sixties, his other shop in Manor Park closed in the mid seventies. Rory himself sold the business some years back, and it was latterly owned by the John's of Romford motorcycle chain before finally ceasing to trade three or four years ago. Rory was a member of the Easterly Road Club, and he was probably the premier dealer for club cyclists in the East London and Essex areas for many years, the Manor Park branch resembled a clubroom on a Saturdaymorning, packed with cyclists. His frames were widely used by local riders, and it was rare to come upon a clubrun on the Essex roads without at least one Rory in the peleton. The frames were not made on the premises of either shop, being built on an industrial estate in nearby Dagenham for at least part of the time. They were well regarded as a good quality frameset, even non-cyclists would often be heard to exclaim "Wow look, a Rory o'Brien".
Quality bike so worth spending a bit of time and money on it