It ended with a boat. That's the part nobody puts on the poster. The first Orient Express left Paris in 1883 bound for the Black Sea, and the passengers did not sit in their berths all the way to Constantinople, because the rails simply weren't there yet. They got out at Giurgiu, crossed the Danube by ferry, boarded a second train on the Bulgarian side to Varna, and finished on a steamer across the Black Sea. Three modes of transport and a great deal of luggage handling. I find that enormously endearing.
Wagons-Lits were Belgian, and they did the thing properly anyway. Sleeping cars, a dining car with a real kitchen, and a conductor per carriage who stayed with his coach the whole way and more or less ran a small hotel out of a corridor about as wide as your shoulders. Those men knew every customs post and every border guard's name. If you've ever watched a sleeping-car attendant make up a berth while the train is doing seventy, you know it's a craft.
The through route to Constantinople came later, once the Bulgarian line was finished, and after that the thing got its reputation — novels, spies, the lot. But I'd rather have been on the first one, standing on a Danube quay at some ungodly hour with a porter telling me the steamer's running a bit behind. It usually was.
Harold, that first dinner out of Paris is the bit I'd queue for — oysters, soup, turbot, chicken, beef, game in aspic, then pudding, all of it off a coal range in a galley you could barely turn around in. Carrying a sauce down a swaying corridor in 1883 and not wearing it is a craft too.
Harold, the whole Paris to Constantinople run came to roughly 80 hours when it worked, and the Varna steamer leg was a night's sailing across the Black Sea on top of that. Every transfer means hands: ferrymen at Giurgiu, porters at Varna, stevedores at the quay, all moving trunks that weighed more than they did.