Camouflaged Lancaster GR3?

Just watching some rubbish programme about UFOs but amongst the random film clips, I spotted some footage of a Lancaster GR3.

It was carrying the SMR unit marking (St.Mawgan/St.Eval) and also had the rear twin windows in the fuselage, so it would appear to have been a GR3. But it was camouflaged. Very odd – I don’t recall having seen a camouflaged machine before. Anyone know more?