Actually the centre one is very much to do with emissions control...
I can't quite say that "every" car of this era had some form of airflow control, that did not involve induction scoops, in order to adjust the mix of hot and cold air introduced to the carburettor. But I know that Rover did not invent such a concept, and many, many cars, in many markets across the world, had such a feature.
The only real surprise here is that even late British four cylinder p6s did not (but you'll note that the air box inlet on four cylinder cars goes almost to the radiator).
The most common form this takes is a valve in the air filter inlet, that alternately takes in cool air from somewhere towards the front of the engine (where there is cooler incoming air) or from a path above the exhaust manifolds. These often also have a vacuum function, that moves the valve on accelleration.
On a modern (or even ancient) car with a turbo, it is known that cooler air is more efficient at boosting power (I suppose because it is more dense than hot air), so you will find air routed from the front of the car, or underneath, to the air filter box – rather than taking air from the within the engine bay.
Hmm, well, that's a lot of hot air expended.