Rear Air Conditioning on Range Rover

I just saw a few Range Rovers with rear air conditioning units.
It is mounted opposite the Spare tire, takes up about the same space. I cannot figure our how it is getting its cooling. Looking under the car I see no hoses going to the front, not evaporator etc.
Can anyone tell me more about these? How do they work? What years did they come on. The ones I saw were on '90's Classics.
Where can I find some information on these?

Thanks for your help,

Gregor