The crossover will be Country end of Charlton.
There is already a crossover Country end...
TL425 + TL427 are getting new Junction Indicators to take you from the Down North Kent. We have been told to accept it as a normal signalled move. Wrong side into Charlton and back across at TL443 (Country end of Charlton) From what our brief was saying was if there is a unit on platform 2, this will allow you to pass via the up platform. On my map it looks like this will signal you through the existing shunt move (852A/B points)
But I’m not sure that is the plan.
Is there a plan ? That is where the derailment happened a few years ago. (the London end shunt)
The crossover primarily enables you to turn back up trains and send them back down towards Dartford. As you can bidi along the Up line, you can terminate a down train, and send it back towards London.
We do this already, although I haven't done it for a long while now. It's another rare one. For it to become a new, potentially regular move I am a little suspicious. The rarity doesn't seem to justify installation of a new ground position signal and allow a 12-Car turnback, which should still require a second Driver.