Armoured panel ID.

[Gil Boyd]

I believe they moved over to tracer at the same time as armour piercing rounds when they were having a real job hitting the night fighter targets at night from the rear of the Lancs. This was the same time they trialled taking all the perspex out to give the gunner the very best night vision possible to seek out the silouhettes coming at them to then relay to the Skipper to deviate his course left or right.
There were also lots of technical gizmos in the tails of the Lancs which worked fine for a while I remember my dad telling me, but towards the end of the war the Germans used the radar beacons to locate the bombers. Can't remember its name I'm afraid, hands sore from clapping for the NHS and one too many beers I'm afraid