Certainly Britannia ran troopers all through my time. (80-94). Usually as a double, so 4 sectors instead of our usual out and back. Gave rise to the riddle
" What's got 4 legs and F*cks the cabin crew? A double trooper. "
They were later linked to a Belfast schedule, as level bust says, but I am sure that was not until the early 90's.
The Belfast schedules were always full, and it seemed to me that Brit missed a golden opportunity to expand on that. In 93/94 they got rid of their 737's at knockdown prices and paid a lot of money to a lot of pilots (me included) to accept redundancy.
With the ecomonies of scale they had, if they had used those pilots and aircraft to expand into lo-co schedule Ryanair would not have grown as it did, and Easyjet probably would never have started. As it was, Easy started with two ex Brit leased in 732's, and Ryanair had the 6 newest of the Britannia fleet.
Not only did they sell the aircraft of cheap, some numpty decided to sell of all the parts and funnily enough Boeing aircraft use the same fasteners on 737, 757, 767's. So back to the company they were flogged to and pay a shed load of money to get them back.