During the past three decades, Paula Radcliffe has covered more miles by foot than many have by air. Now, though, she has almost no distance left to run. Next Sunday she will slip on those impenetrable wraparound shades, stretch her rickety achilles, and then – after the pop of the starter’s gun – begin her final 26.2-mile journey through the streets of London. Two-and-a-half hours later, her competitive career will be over. No more cheers or tears.

Last year 750,000 people watched Mo Farah struggle through his first marathon. Organisers expect similar crowds again to hug the streets from Greenwich to the Mall, and hope the hashtag #thankyoupaula trends on social media. Does Radcliffe need thanking? I’m not sure. What she undoubtedly deserves, though, is a rousing send-off – and overdue recognition that she is one of the greatest female distance runners in history. Perhaps the greatest.

Certainly her world marathon record of 2:15.25 – set 12 years ago – is every bit as staggering as Bob Beamon’s 8.90m long jump or Usain Bolt’s 9.58sec 100m. On that day, her average pace per mile was five minutes and 13 seconds. Try sustaining that for 385 yards, let alone another 26 miles. Radcliffe holds the three fastest times in history – the fourth, by Kenya’s Mary Keitany, is over three minutes slower.

In 2003, the year of her marathon record, Radcliffe also won her third World Championship half-marathon title and set world road records in the 5km, 10km and half-marathon. In her peak years, from 2002 to 2008, her races usually followed a simple equation: if she was fit, she won.

We live in a climate where extraordinary performances are greeted not only by dropped jaws but by arched eyebrows. Rightly, too. But as far back as 2002 Radcliffe was urging the IAAF to randomly test her blood and urine more frequently, and asking for samples to be frozen so they could be back-tested when better technology emerged. She called for blood profiling seven years before the biological passport was adopted.

Radcliffe was also blessed with incredible genetics. As David Epstein points out in The Sports Gene, when she was tested at 17 she had a VO2 max “essentially as high as elite female athletes ever get”. But these natural gifts were matched by an unrelenting work ethic. She ran 140-150 miles a week, and spent three to five hours each day doing physical therapy, massage and ice baths. Athletics wasn’t merely a full-time job; it was a 24/7 existence.

And it wasn’t only on the road where she dominated. Elite coaches often say how hard it is to excel across road, cross-country and track, because of the different demands they place on the body. Yet Radcliffe won the world cross-country championship twice – as well as European and Commonwealth titles and a World Championships silver medal on the track.

True, her track career wasn’t quite as successful. In the Atlanta Olympics she was fifth in the 5,000m, while in Sydney she was fourth in the 10,000m. Getting swallowed up by the chasers on the last lap – and those “Brave Paula” headlines – became as much a part of August as the new football season. But – crucially – most of her track career came before she started working full-time with the Irish physical therapist Gerard Hartmann.

As Hartmann explained to me, because of her poor posture, weak core and erratic running style, Radcliffe would run her last lap in 67 seconds, while others such as Sonia O’Sullivan were several seconds quicker. It took Hartmann 18 months to sort Radcliffe out, reducing that last lap to 61 seconds. Admittedly, the head bobbing wasn’t completely eradicated, but by 2002 a stronger, smoother Radcliffe ran a 10,000m personal best of 30min 01.09sec – the sixth fastest in history, and a time unsurpassed for six years. It is quite likely that more medals would have followed on the track. By then, however, her attention was on the marathon.

Hartmann also has a riposte to keyboard warriors who accuse Radcliffe of lacking bottle by stopping on the road to Athens in the 2004 Olympics. Three weeks before the race, she was running in Portugal when she suffered a freak accident: a passing car on the gravel trails flung a stone which hit her knee joint and led to a deep abscess. Not only did she miss two-and-a-half weeks of training but anti-inflammatories left her dehydrated and played havoc with her stomach.

“The tragedy is that she was physiologically in 2:14 marathon shape,” says Hartmann. We never got to see it. During the race she had violent cramps and had to empty her bowels on the road. “She got to 22 miles still in a medal position but her body shut down,” adds Hartmann. “How she got that far I don’t know.”

Seen in this light, Radcliffe’s performance in 95-degree heat and stifling humidity was not an abject failure, but an act of desperate courage. She further showed her character by winning the New York marathon 11 weeks later. The following year, she won at the World Championships too. Bottle? That’s one thing she never lacked.

Such victories are long behind her. A degenerative injury causes Radcliffe’s left foot to not pick up properly, and so her times do not reflect her effort. It means that in London she will start with club athletes rather than the elite field. She has promised to try to revel in the moment, however disconcerting it feels. Those watching will ensure the last vestige of her career is a living, breathing, joyous memorial. It could be generations before British athletics sees her like again.