A 1928 film called Underground holds the key.
''Stand on the right, walk on the left'' has always been the golden rule on escalators.
Anyone who uses the tube will have heard it a thousand times and woe betide if you get it wrong.
If if you've ever wondered why we do it, and why so many tourists get lost in translation, the answer may lie in a piece of film from the 1920s.
Underground is Anthony Asquith's 1928 classic where passions run deep in a tale of jealousy, treachery and even murder.
It was partly shot at Waterloo station and it was one of the first times the Tube system had appeared on film.
The escalator design had a diagonal step-off, clearly meant for the right foot first so standing on the right made sense.
Marc Ashdown talked to a number of tourists using the Underground system to see how they were adapting to our escalator etiquette.
Film footage of Underground courtesy of BFI National Archive.