My only experience of the Varsity was an air experience flight from Stradishall when I was in the ATC in the 60s. Oddly I am now helping to restore that very aircraft at Brooklands museum. If anybody out there can help with a picture of a monitor for the Rebecca system that looks a bit like a telescope poking out of the nav station, I would be grateful. There is currently a replica device labelled as such made from an old plastic milk bottle!