This is worth a listen:
http://www.bbc.co.uk/programmes/b0105ymz
Personally I'm doubtful. Not that I'm an expert. And if GHS and PR think it's possible maybe I should just concede to their opinion.
Last year I watched a road race on telly. Not something I do that often. I saw Joseph Ebuya (the world cross-country champion) run 10 miles (The Great South Run) in 45:16. That's 4:32 pace. And my jaw was on the floor. It was mesmerising. And to expect somebody to run 4:35 for 26.2 just seems too much.
50+ years I reckon.