GC catering staff and guards do the clear up themselves mostly en route after Doncaster or York, but yes a fast turn around especially given there is also an operating crew swap between units, as the drivers and guards don't operate both routes.Decent turn around job on 1A66 into 1D97! Just over 15 minutes to unload the arriving passengers, load the departing passengers, close up and dispatch! Not bad on a long distance service. I've seen LNER (or a predecessor) do one of their sets in about 20 minutes including a very quick litter pick and catering restock which I'm assuming that GC had to skip on this occasion!
It may have helped that both crews are going home, and probably wanted to escape the chaos of Kings Cross as quickly as possible!