“Most people could do 1,500 and 5k, 800 and 1,500, or 400 and 800, but I can run a pretty good 400 and a pretty reasonable 5k,” she admits. Others could run both of those, but not as quickly as I could.

If there was such a thing as a running pentathlon, I’d be right in there.”Given her ambitions, Muir’s repertoire is invaluable, firstly because it increases her options.

When it occurred to her that a place on the GB team for the World Championships would not be easily secured in the 1,500m, she went to Belgium for an 800m race in which her performance was so impressive that she was selected for Moscow. As well as stamina, she has pace, and quite a burst of it at that, which is rare in distance runners.

If the race goes off fast, I’ve still got the endurance.

Either way they run it, I’m going to be OK.”Andy Young, her coach at Glasgow University Athletics Club, can take much of the credit for Muir’s development, but in many ways, she is a freak of nature.

He talks about the acceleration that distinguishes her from other athletes, and the fast-twitch fibres that give her more than just an engine.

When it comes to the 20-year-old athlete from Milnathort, whose extraordinary versatility has singled her out as Scotland’s most exciting prospect in years, anything seems possible.

At the IAAF World Championships, which start in Moscow on Saturday, Muir will run for Great Britain in the 800m.

Not bad for an athlete whose focus, in her first year at senior level, was on the 1,500. It has reached the stage where even she is not sure.

In Barcelona this week, where she will be in the squad’s holding camp, she might care to reflect on her visit to the same city a year ago, when she ran 3,000m in the world juniors.

Muir has always combined speed with endurance, but her priceless ability to do so came into its own two years ago, when she started a veterinary degree – and a new training regime – at the University of Glasgow.

If she was not winning national 400m and 1,500m titles on the same day, she was following victory in the Scottish under-20 cross-country championship with an indoor 800m title 24 hours later.