Re. Bentley Speed Six "soup pot" - that is the supercharger. Basically, an engine-driven pump to force more fuel and air into the carburettors and increase power. Power increase is basically linear with engine revs, which can be interesting when you change gear.
A similar system to the turbocharger, which uses exhaust gas pressure to drive the pump. Robs less power from the drivetrain (insignificant anyway) but power increase is dependent on exhaust gas pressure, hence the "turbo lag" while the pressure builds up before all hell breaks loose. Modern turbos are better than my dad's old Saab 99 black one.