Firstly I also wondered if this was a 'maritime' lancaster in Coastal white - regrettably I can't find any pictures of similar ones, so don't know exactly what colour scheme they used post war. An additional point is the projection you highlight looks like the 'trailing aerial' mount that we still had on the MR Shack (wound out fully for HF comms - about 100-150 ft IIRC - it was also a good rudimentary radalt; if HF comms were lost you were too low!). It also has what look like early SARAH or similar homing aerials mounted on the nose - another pointer perhaps to a maritime version.
Secondly the props almost certainly look feathered, and I suspect in the days before photshop it would have been impossible to fake. There were plenty of tales doing the rounds when I went through MOTU and first Sqn of Shacks diving to get lots of IAS, then feathering all four for a fly past and unfeathering before the speed ran out to climb away again - Gibraltar Air Days, Biggin Hill and other RAF Open days, although I never met anyone who said they had actually done it. It didn't even require much airspeed to unfeather the Griffon - about 80kts to 'bump start' one when we had a starter motor failure at a very remote airfield in the Far East, so the Merlin should be even easier . As for the flame traps, they were very welcome for the crews during long overwater flights as the continuous flickering/glow from the open exhausts could be quite distracting.