That film is largely about how information flows around a 24 hour event. Sam, the main character in it was the winner's team boss for two successive years. Unfortunately he passed away last year, so apologies to those who may find it a bit too poignant.
His rider was unknown in '24' circles but known at other distances. The guy we talk to about number 85 being the fastest at 100 miles is Andy Wilkinson, the current UK record holder at 541.17 miles.
I'm still confused by Sam's downcast attitude with 3hrs and 15 mins to go. They might have got the timings wrong. The course is laid out so that the fastest three riders will do all the legs, and slower riders will have sections omitted. No 85 was so fast he did an extra leg. The course isn't a circuit as such, so you've got to be very aware to know what is happening.
The end of the day is on a finish circuit. Once the rider is on that it's just a case of finding out what their mileage was when they entered the circuit, and how fast they are going. There are timekeepers at approx 2 mile intervals around that circuit, and riders have to reach the next timekeeper if they pass one before 24 hours is up.
The finish of the first rider is the important bit to film, but It can be at any of 6 locations, so I need to know a lot about how they are going. We devoted quite a lot of energy to filming the 24 in 2015, as we were testing an approach for filming PBP 2015.
https://www.youtube.com/watch?v=yeRBvJ4cMZkPeople tend to take things for granted after a while, and seem to think it's merely a question of pointing a camera at the subject. But it involves a lot of mental arithmetic, but so does timing applications of paint, which is when knowing how fast paint dries is a core skill.