"Take off from the centre of London, land in the centre of Paris, 1 hour door to door. No faffing about with taxiing etc, and very little airport infrastructure or space needed."
So about a four hour journey with security etc. I don't think there is a market left for such a journey, hasn't 90% of flights been replaced by Eurostar? Similar situation with Spain, high speed train and completely replaced air travel for certain journeys. EU policy will encourage this in future.