Thank you for your posts - I finally got the simple answer I needed. Perhaps I was a little naive in thinking that it was a simple question. Our American friend that did not read the question really made a meal of it - I suspect he is a Microsoft pilot or is very new at the game.
Meiklour - I was still at Glasgow when they took the Vanguards of the route - it was not until we got the T3 with 140 seats that we had the same capacity - the fuel load for the T3 was double that of the Vanguard for a journey time only a few minutes shorter. The Spey was very good at turning fuel into noise! BAC 1-11 with no acoustics was something else,I sat on top of one at max power for a leak check - only once.