In 2018, Cockram, who grew up on a farm in Cwmbran, near Cardiff, ran two more marathons in her trusty pale-blue discount shoes. But they were getting old, and the runner was growing curious. The day before the Houston Marathon in Texas, the following January, she found a pair of Nike’s new Vaporfly 4% shoes. They had bright orange uppers above thick white soles that looked like little marshmallow lifeboats.

In Houston, Cockram pulled her personal best down by 90 seconds to 2hr 34min. Nine months later, she came fifth at the 2019 Dublin Marathon, breaking the 31-year-old Welsh women’s marathon record with a time of 2hr 30min 50sec. That Cockram had run so fast, only two years after taking up the distance, gave her hope that she could qualify for the Tokyo Olympics.

Eighty seconds short of the elite athletes’ qualifying time, Cockram began targeting the 2020 London Marathon. By then, her flashy new shoes, which are notoriously quick to wear out, needed replacing. They were also outmoded: while its competitors scrambled to catch up, Nike had released even more outlandish models. The latest – the Alphafly Next% – was ready in time for Kipchoge’s second, by Nike and Exeter University of the Breaking2 athletes revealed that they succeeded thanks, in large part, to their extraordinary ability to manage oxygen intake efficiently while operating just below the exertion level that results in terminal fatigue – or “hitting the wall”, in endurance speak.

But under mounting pressure last year, World Athletics (formerly the IAAF), agreed to investigate all new long-distance shoe technology. In January this year, it announced new rules. Any competition shoe had to have a maximum sole height of 40mm and contain a single plate. To ban secret prototypes, shoes would also need to have been available for sale for four months. (The rules don’t dictate how “available” a shoe should be.)

The rules were good for Nike, stopping short of outlawing any of its new range (it denied rumours, based on a patent filing, that Kipchoge had broken the two-hour barrier on prototypes containing three carbon plates and a sole height of more than 40mm). Pitsiladis was dismayed. He believes that Tokyo, now delayed until next July, will go down as “the Games that killed off distance running”. He’s also concerned about the effect of Nike’s innovations on the track, where records at shorter distances are also being smashed using other lines of shoes based on the same technology. “Someone’s got to do something,” he says.

But Nike are not the sole innovator in super-shoes. The brand’s rivals, including Adidas, are locked in a frantic race to catch up.

One morning in early September, Sam Handy was standing at the socially distanced finish line of a half marathon in Prague. As a rare opportunity to run after months of cancellations, the elite-only race attracted some big names. Handy had eyes on one runner: Adidas-sponsored Peres Jepchirchir, a Kenyan former women’s world record holder at the distance.

“What Peres did was remarkable,” says Handy, still buzzing. “We feel we’re in the game in a big way… It’s all back on now.”

Pitsiladis is sceptical about the levelling effect of these rival shoes. “You’d be making a big assumption that all companies can equally finance the developments required,” he tells me. Even if startlines become equal again, he argues that expensive, barely obtainable shoes threaten the democracy of running – the very reason that gifted athletes, often from poorer countries, have been able to propel themselves to glory.

Handy says Adidas plans to release greater numbers of the Adios shoes, which have also sold out at record speed. “But this is not a shoe built to democratise running,” he adds. “It’s about allowing a pro athlete to stretch the limits of performance.”

The victims of the arms race seem to have been those athletes stuck in the wrong shoes. Wilson Kipsang and Kimmetto, the last two world record holders before Kipchoge, have faded in Nike’s shadow. Other hamstrung athletes have looked for ways to fudge – or even tear up – their sponsorship deals. Nike shoes taped up in black to disguise their logos have become a common feature of elite races. Smaller brands have compromised, allowing their runners to wear Nike shoes: better to have fast vests than slow everything.

After acquiring her own pair of Alphafly Next% for the London Marathon, Natasha Cockram soon had more to worry about than shoes. Days after her best-ever training session, her right ankle exploded in pain. A scan revealed a cyst on a ligament. She couldn’t run for three weeks before the event. “I was convinced it was over,” she says.

Two days before the race, with a supply of pre-approved painkillers, Cockram checked into a secret hotel in Windsor. All athletes were required to quarantine before the race, which was for