Can someone explain to me in plain English about the towing weights and restrictions

I have read the RSA website but still not sure.

I suppose what I want to know is could an e34/e39 tow an e28/e36 assuming you had a BE licence?

I see the BE licence limit is 3500KG - does that mean the car towing, the trailer and the car on the trailer must not exceed 3500kg?

At what point do you need a jeep to use for towing?