Mindweak reckons that Bannister invented EPO, so it's possible that a sub 4 minute mile has never been run clean....according to him.
Don't know if he has read the following article - he might have to start claiming that the dastardly Brits invented EPO in the 18th century.
https://www.theguardian.com/sport/2004/may/02/athletics.comment1