I'm old enough to say I travelled on Tait carriages on a daily basis - swing door and sliding. During the change-over, when a blue (Harris) train came along, with its double doors, the relief was almost palpable - oh, the comfort and the bliss. On hot days, there was much more moving air entering the carriages. Yes, in both Tait and Harris carriages one could have the doors open while in motion - not in the swing door versions though. Seeing these carriages in the modern era is certainly evocative of memories of those days of old. I don't remember the window frames being painted cream though.