That'll be a caravan - one connector for the lights and one for the van electrics (interior lights, fridge etc) . .
No Caravan on there drive though which is strange..nor connectors on the other car.
Its been sitting with no MOT for nearly a year but looks like they still clean it although it never moves
Been hoping to catch them on the drive whenever I walk past to have a chat and find out what the deal is but no dice