I’m a average/ good runner, I can do a 5:45 min mile and my best ever 10k time is 39:45. I know guys that are really really quick who are doing 35-37 mins for a 10k ( this would win most club events)
Mo farah can give me a 10 minute head start and still beat me, comfortably by a couple of minutes, and give some my mates a run for their money.
Once for shits and giggles being measured for speed by my son on his bike I tried to see how long I could keep up the 13mph it takes to do a 2 hour marathon, it felt like I was having to sprint!! Lasted about 400-500m at most!!