This is yet another example of how Land Rover drove people away from their products. What sor tof masochist will stay with a marque when they've had a P38?
On-board battery chargers are absolutely necessary with P38s if they aren't driven regularly. After the second time of locking the keys into a P38, I now only change batteries with a door open. Also, be very careful when changing batteries on P38s, I've replaced several BeCMs due to problems that occurred during battery swaps.
As for how to remove the cables, lots of Kroil, PB blaster, liquid wrench, etc and then, there are tiny little two-jaw pullers that work well in these situations. Plan to replace the cables as they may be corroded inside where you can't see it.
Yes, I am still alive, and still in the Rover parts business.
Text me for greatest likelihood of finding me.
Dominic Perodeau/Global British is a thieving bastard, do not send him money.