Hi again Stuart and my guess is one is for the trailer brakes and the other is for some sort of power supply.
Don't be surprised if it is wired up as a quarsi dual battery setup or 3 way fridge supply.
Note, the maximum size fuse/circuit breaker for safe use on 6mm AUTO cable is 30 amps but auto electricians regularly use 50 amp CBs and then wonder why they have fires.
Also worth checking where they have run that cable.
It looks like it may be run down through the chassis rail and if so, you will need to remove it, because if you ever need work done on the motor, they take a few bolts out and lift the body off the chassis, cutting any wire/cable running through the chassis.

