Would this have been related to the Canadair CL-40 or CL-50 projects ? as well the Britannia 600/Type 187.
Bristol/Convair/Canadair Joint Project
With Bristol thinking they could not handle a project the size of the 187, discussions were also held with general Dynamics (Convair) and Canadair during 1955/56 over the development of the 187. The new study was to be powered by four Bristol BE25 series 2 engines and would accommodate up to 150 passengers at six abreast on two decks, within a fuselage diameter of 13ft 8in. The mid-wing monoplane would have a range of 5,300 statue miles (4,600 nautical miles) and would operate the Transatlantic non-stop with a 25,000lb payload. The proposed all-up weight was put at 205,000lb.
It was envisaged that the maiden flight would take place in January 1960, with entry into service by April 1962. BOAC were interested in the proposals early on, as they featured a double-bubble fuselage. However, the government was not so ken, especially as it appeared that Bristol and the UK would have ended up giving a lot of technical knowledge to their American rivals. Design and production would have been split with Convair at san Diego having design responsibility, including production drawing, wing design and system and fuselage detail. Bristol would have been responsible for fuselage layout, stressing and general structure, manufacturing the fuselage and tail while there would have been two final assembly lines, one at Filton and the other at san Diego. The Bristol BE25 would also have been built under licence in America.
Info from here:
http://www.alternatehistory.com/Discussion/showthread.php?t=126337
Regards Bailey