I recall an M.I. story from Uncle Tom, who was at Le Mans back in the mid 1950s.
He was standing at the start / finish during one of the practice sessions. M-B was a bit slower than what they were expected to show as far as lap times. They would pull the car into the pit, mess with it and go out and maybe gain a few seconds - not much with such a long lap.
Tom, bored, started driving about the area, stopping whenever he saw something interesting. About half-way around the track, he noticed a lonely MB sedan parked near the course with two men in it and a whip antenna.
Tom suddenly cottomned onto that MB had set up their own timing section and was running one fast, then one slow lap, using the sedan as the marker.Those timing at the official pits were seeing a laps consisting of half a slow lab coupled to half a fast lap, whereas the M-B pair in the car timed a fast lap followed by a slow lap, thus hiding their true speed.
U.T. didn't let on to anyone, but I wonder if he made a bet based on his knowledge.
Karl