Guys the engine in that car is a 4 litre, 6 cylinder Austin engine, same as used in the Jensen 541, a predecessor of the Interceptor.
It is also sometimes called an A135. A guy in the Triumph club, Vic Whitmore, has one in gold which he uses as a wedding limo.
I have never been in one though I have ridden in a Daimler 4.5 litre V8 limo, which is similar. They have neat little fold-down seats mounted against the partition separating driver from passengers, these face the back seat as on a train.
Simon.