How to change gear on a Brompton folding bike

We often get asked "how do I change gear on my Brompton?"
This is especially common on a 6 speed Brompton where it uses a combination of the 2 speed derailleur and the 3 speed hub gear to give a total of 6 gears
In this video we show how to change, when you should and shouldn't pedal and finally give a demonstration ride