The Magnum Britannia is a big, mostly handmade ultra-luxury sedan.
It features handmade, all leather trim, the nicest interior possible in the mid 80s, a strong and reinforced body and an "7 1/4s" engien, meaning it has a long stroke V8 with 7.25l of displacement. That engine is set to comfort and torque, because the car is heavy and the power goes to the rear wheels through a 4 speed torque converter. How much power? Enough. We wont tell you.
The Britannia Turbo is the car version of "more than enough" featuring stuff like a Televison and even nicer comfort. Also, it has a twin turbo V8, just for more torque and if needed, a bit more punch when flooring it, for example to get away from paparazzi (Quote from 85, didn't age quite so well....)
If you prefer driving yourself, the Eden might be the car for you. It is a coupe version of the Britannia with a more conventional, slightly sportier suspension and better handling. It always came standard with the turbo engine and was especially popular with "new wealth" people, as the "old money" preferred being driven.
If "more than enough" wasn't quite enough, and you were some kind of eastern oil magnat, you could opt for the Eden sport, that was mainly made because some of those oild princes and kings asked for it. It ahs less stroke and therefore a 6.75l engine, but that allows it to revv much higher. Also, the engine is far less restricted for comfort and therefore can unleash its full potential. It has awd and a manual gearbox because automatics of the time had issues with the high torque and power output.
Please keep in mind that you are driving a 2t luxury car with a "comfortable" construction, it doesn't handle like a sports car even though it's really fast. The laws of physics still apply.