A Roman legion was on the march...
...left, right, left, right, left, right, left, right, left, right, left, right, left, right, left, right, left, right, left, right, left, right, left, right, left, right, left, right, left, right, left, right, left, right, left, right, left, right, left, right, left, right, left, right, left, right, left, right, left, right, left, right, left, right, left, right, left, right, left, right, left, right, left, right, and so on (ad nauseam) (no, that's not the joke). Suddenly the general at the head of the vast column shouts "HALT" and the whole army comes to an immediate stop - all except for one little bloke who trots all the way from the back of the column to the front.
The general shouts, "You 'orrible little man what the @$**#@g *@#l do you think you're doing? I shouted HALT!"
"Sorry guv", panted the lttle man, "I thought you shouted 'Walt'."