The classic cars you can see here have one thing in common: They are equipped with a preselection transmission system, built by Wilson, Cotal and ENV.
And that´s how it works: First choose the gear and, when time has come, just activate the clutch.
These kinds of transmission systems had been used in the 30s in many sports- and racing-cars, and also – just up to the 60s – in the British double-decker buses. That´s the reason why there were so many cars which had preselection transmission: Alvis, Bugatti, Delahaye, Delage, Hotchkiss, Invicta, Lagonda, Salmson, Simca, Talbot, Ford, Peugeot, Renault and also Citroen.