The Tristars were delivered in 1972 and were mainly used round Europe. As already said they did operate to St Lucia, generally via Bangor.
They were also configured like Caledonian's and carried 400 passengers. Unfortunately I can't remember seeing one take off going to Bangor, as I was still at school. The only time I flew on one was to go to the Paris Air Show, so we didn't have a lot of fuel.
When Court Line went bust one of the Tristars was on the ground at Bangor, but they got it out before the authorities realised.