Historical document: Paris to London "Train + Air" Service.
The passengers travelled first by fast DMU train called "Flèche d'Argent" (Silver Arrow) from Paris to the coastal city of Le Touquet, then by plane from Le Touquet to London Gatwick airport. The train ran directly to the airplane, on the airport tarmac. The connection just required a short walk between the train and plane. (Not sure how today's security standards would allow that!)
The service, the RGP series DMU and the aircraft are all gone now. The Flèche d'argent Train+Air service ended 1year later, in Sept 1980. Even BIA, British Island Airways belongs to history. The aircraft is a Handley Page Dart Herald 200, a series dating from the 1950's, that was in passenger service until 1987 and in freight service until 1999.