boat train

I read that a boat train is a passenger train which connects with a passenger ship but I do not get the meaning in this sentence :

"Allen spent two weeks in London beginning February 2, when he crossed the Channel to Dover on the Boat Train." (This is in the 1950s.)

Any idea ?

Both boats and trains existed in the 1950s. A boat train could be a train which continues onto the boat or, more likely, a system where you catch the train, then the boat, and then the train again. I would say you have understood perfectly.

Yes I remember this - they used to put the train on the cross-channel ferry (even the Orient Express) - the deck had railway lines on it and the passengers continued sleeping in their sleeping compartments (it wouldn't be allowed now)

Thank you ! Do you know how to call it in French?

Hello,
While the "boat train", from the '60s until now, is used for the journey where one takes the train from London, gets of at Dover (for example), joins the herd to queue up with one's luggage to get on a boat and on arrival at Calais repeats the process to get on a train to Paris.
From what I remember of the "boat train" in the '50s one waited hours on the train at Dover while they put the train (carriages) on the boat and then waited again while they took them off at Calais. At least one was sitting all the time.
Which was better? Lugging all one's bags up and down steps and queuing or getting an aching bum waiting for something to happen?

PS franc91 answered clearly while I was having unfond memories.

J'ai trouvé - le Night-Ferry
http://www.questmachine.org/article/Night-Ferry_(train) (paste it in)

"train faisant correspondance avec le bateau.

Hello,
On a site devoted to the history of sleeping cars/wagons-lit one finds:
"Les voitures-lits type F, apparues en 1936, ont été conçues pour le service direct Paris-Londres avec transbordement sur train ferry (Dunkerque-Douvres)."

Thank you!!!!