Ah the secret RB-178 engine turbofan prototype which was originally known as the "Super Conway". This was the first large three-shaft commercial high by-pass ratio turbofan designed by Rolls-Royce in 1966; it was intended to power the following:-
Hawker-Siddeley HS-132 & HS-134 "projects"
BAC VC-10 DB265 "project". RB.178-14 27,500lbs thrust version. (double decker)
Bréguet Br.124 "project".
Shorts SC5 ./45 "project". Belfast with jets
A 44,000lbs thrust version was rejected in favour of the competitive Pratt & Whitney JT9-D turbofan for the Boeing 747 in 1966 but for the refusal of Boeing to accept the Rolls-Royce engine on the transatlantic 747.
The RB.178 engine was never flight-tested and never went into production as most of the intended applications remained unbuilt "projects"
The RB 207 intended for the abortive original Airbus A-300" project" of 1967/68 - went on to become the RB211 engine first used on the Lockheed L-1011 TriStar