"Good news, chaps - there will now be two shifts".
We had two shifts at Northolt in the late 70s.
Both shifts covered alternate days for 24 hours on a seven days a week rotation. Saturdays and Sundays were "slack time" - you only had to go in for the departures and arrivals. .
That's why I left.
Flexi-time would have been very much appreciated and I might have stayed in.