Next Friday (May 24) is the 30th anniversary of a landmark day in sporting history, a day when, according to the Italian media, Europe experienced the biggest movement of people from one country to another since the Second World War - to watch a football match.

Around 90,000 supporters of AC Milan made their way to Barcelona to watch their team defeat Steaua Bucharest 4-0 in the European Cup Final.

Milan fans ended up with nearly all the tickets for the final, which was watched by 98,000, because the Iron Curtain was still in place and the dictatorial communist leader Nicolae Ceaucescu - who would be tried and executed by the end of the year - would not allow Romanians out of the country.

Ruud Gullit and Marco Van Basten each scored twice, their fellow Dutchman Frank Rijkaard also played a leading role, and Milan’s success prompted Italy’s top clubs to go on a spending spree for foreign talent.

In the early hours of the same day there was another remarkable sporting achievement, by the Greek-Australian ultra-runner Yiannis Kouros.

Kouros ran one of the most impressive races in the history of running but because it was an ultra event, a test of endurance from Sydney to Melbourne over several days, his achievement made little impact in the media and has been largely forgotten.

If you make a google search for the 1989 European Cup Final you will have 28 million results; do the same for Kouros’ race and there are a just a few thousand.

Even a general search for the words "Yiannis Kouros" produces a mere 57,000 results.

Unless you are an ultra-running aficionado of a certain age you are unlikely to have heard of the man known as the "Running God", "the Master of Pain", "the Colossus of Roads" and many other names.

Given his achievements that is a pity, but it is perhaps not surprising given that Kouros was interested only in extreme distances, and he killed excitement at the finish line by sometimes winning races by more than a day.

Race reports featured lines such as "the field was strung out over 300 kilometres"; when he finished one of his 1,000-mile races the man in last place was 480 miles behind.

Although ultra-running is deemed to be anything longer than a marathon, Kouros cares only about races of 100 miles and upwards, or 24 hours for events measured by time rather distance.

Anything below 100 miles was "just not challenging" for a man who said, "No one completes the race via his body but via his mind.

"When other people get tired, they stop. I don't. I take over my body with my mind. I tell it that it's not tired and it listens.

"The pain is the reality but your mind can inspire you past it.

"I look to the countryside, music, and art to help inspire me."

Marshall Ulrich, the American ultra-runner, adventurer and mountaineer who wrote Running On Empty - and whose google score is way over 10 million - acknowledges Kouros' greatness and says he is "one of my heroes".

Ulrich wrote in an adventure sports journal, "When I had a chance to meet him in 2005, we talked about this weird experience I had once, where it felt like I’d left my body.

"It was as if I’d hovered over myself, devoid of pain, about 60 miles into the Badwater Ultramarathon. Was I hallucinating? It didn’t seem like it. I wanted to know if this had ever happened to him.

"All the time, he said. This happens when you’ve kept going beyond your breaking point…He considers this a supreme experience, even a spiritual one.

"For Yiannis, ultrarunning is about transcendence."

Kouros was unbeatable, at least until he passed the age of 50, and still is in some respects at the age of 63 - because his records are unassailable.

When Kouros set the 24-hour track distance record in Adelaide in 1997 he said. "I will run no more 24-hour races. This record will stand for centuries."

At the age of 41 he covered 303.5km (188.5 miles), running the equivalent of seven straight marathons at 3 hour 20min pace, non-stop.

No other man has been within 26km of that record before or since.

The women’s world record fell last year, to the American Camille Herron, who covered 260.9km (162.9 miles) in Phoenix in Arizona, and found herself in a wheelchair for her journey home the next day because of her exertions.

Herron’s great inspiration is "Yiannis Kouros, probably the greatest male ultra-runner of all time".

There is no "probably" about it. Kouros set more than 160 world records according to his own website, which states  "all these records remain unbroken", though it has not been updated for several years.

He set world records on road and track at 100 miles, 1,000km, 1,000 miles, and for distance covered in 12 hours, 24 hours, 48 hours and six days. Most of those records have never been seriously challenged.

Even in his mid-50s he covered 550 miles in a six-day race.

His achievements were laid out by Ian Cornelius, a former President of the Australian Ultra Runners Association.

Besides holding that 24-hour record Kouros is number one at 48 hours covering 473.496 km in 1996, six days with 1,036 km in 2005, 1,000 km in 5 days 16 hour 17min in 2005 and 1,000 miles in 10 days 10 hours 30min in 1998.

Cornelius points out that only seven runners have ever bettered 275km in 24 hours - the other six all did it once, Kouros did it 15 times.

His superiority over rivals is similar in other events.

The four fastest times in the Spartathlon, the historic 246km race in Greece in which he first made his name, have all been recorded by Kouros.

He has set course records in too many countries to mention, and yet he has found time to showcase his artistic talents by  composing orchestral music and songs, writing a collection of poetry and an autobiography in Greek, painting, and starring in a film.

He earned a Masters in Modern Greek at La Trobe University in Melbourne, where he studied two greats of 20th century Greek literature, the Nobel laureate poet Odysseus Elytis, and novelist Nikos Kazantzakis, who wrote Zorba the Greek and The Last Temptation of Christ.

In 1991 he played Pheidippides in A Hero’s Journey, a film about the history of marathon running.

In a message to Kouros on his 63rd birthday this February Cornelius wrote, "You have nothing left to achieve in ultra running.

"Enjoy your new-found love of Greek history and music and rest easy in your retirement from ultra running after such a brilliant career.

We salute you."

On May 24 in 1989 Kouros’ feet grew from size nine to size 11 in the course of the Westfield Sydney to Melbourne Ultramarathon, a 1,011km slog that took in the Hume Highway, the Federal Highway, the Monaro Highway, the Princess Highway and many other roads before it finished at a shopping centre in Doncaster, near Melbourne.

Kouros actually crossed the line second, 32 minutes behind the Australian hero David Standeven, who became only the third man in history to run 1,000 kilometres within six days.

But Kouros, who had first achieved that feat in 1984, was the  clear winner for a third straight year because he started 12 hours after everybody else.

He had won by 26 hours in 1987 and by 16 hours in 1988, so organisers wanted to make the finish a little more exciting.

It was certainly that: Standeven collapsed into his wife’s arms with exhaustion and dehydration after crossing the line and was taken to hospital by ambulance, with a drip in his arm.

After Kouros finished in a record-breaking 5 days two hours and 37min, "he looked like he had just gone for a training run," recalled author Phil Essam in his book about the nine Westfield races, I’ve Finally Found My Hero.

The Westfield race was not eligible for official world records because of the difficulty of precise measurement, but if it had been Kouros would have smashed the 1,000km mark by a long way.

Kouros was cheered to every one of his five Westfield victories by thousands of fans from the Greek community in Melbourne, where he had relatives.

He slept for just a few hours en route, and when "the final surge of 300km"began, according to one report, he was already looking forward to a 12-hour sleep.

He was also looking forward to his body returning to its normal size; it could take up to a week after a six-day race  for his feet and muscles to recover from swelling, and he needed two months for full recovery from his most extreme races.

Kouros ate a lot of carb-heavy food, very little fat, no meat, and sometimes would finish an ultra race weighing as much as he did at the start.

The Sydney-Melbourne Ultramarathon, sponsored by Westfield  supermarkets, was run from 1983 to 1991, after which the sponsorship stopped.

Kouros first entered the Westfield in 1985, two years after he appeared on the ultra-running scene with a phenomenal debut performance in the 246km Spartathlon  - a 153 miles race between Athens and  Sparti, the site of ancient Sparta, that commemorates the run of Pheidippides before the Battle of Marathon in 490BC.

When Kouros crossed the line nearly three hours ahead of his nearest rival there was talk of cheating.

According to one report in the 1980s, Kouros was seen as "an opportunistic Greek who couldn’t possibly be for real", and, bizarrely, one journalist wrote that Kouros had been seen on a motorbike during the Spartathlon.

It was all nonsense, as Kouros soon showed.

He won the 1984 Spartathlon in 20 hours 25min, a record that still stands in the annual event.

The popular American Scott Jurek won three years in a row between 2006 and 2008 but could not beat 22 hours; no other runner has been within 90 minutes of Kouros’ time.

 Kouros started running at the local track in his home town of Tripoli when he was a child, to escape a troubled home life.

His father suspected Yiannis was illegitimate, and the boy suffered for it.

He spent a lot of time with his grandparents, and gained inner strength through running.

He started to make a name for himself when he began competing in the early 1980s, when he worked as a stadium administrator.

With relatives in Melbourne, where there is a large Greek population, he enjoyed his time in Australia and took dual citizenship in 1990.

He built a house for his wife and two daughters, studied at a local university and during that busy time he barely slept - he never needed much sleep.

Making money from ultra-running was never easy, despite his talent, though Kouros did pick up plenty of five-figure prizes.

Disputes over payments led to Kouros refusing to race the Westfield in 1991, when organiser Charlie Lynn said his overall take from the race would have been about AUD$140,000 - worth about £150,000 today.

It irked officials in Australian ultra-running that Kouros competed under the Greek flag, apparently unhappy about money.

Any differences were long forgotten when, last month Kouros was inducted into the Australian Ultra-Running Hall of Fame (AURA).

The AURA was formed in 1987, during Kouros’ Westfield glory days, and was influential in establishing the sport globally.

Nowadays ultra-running, which is becoming ever more popular around the world, is more about trail runs than slogging it out on the roads, partly because of the cost and difficulty in arranging road closures.

"Over the last decade, ultra-running has grown at a staggering rate, becoming one of the fastest-growing sports in the world," says the writer Adharanand Finn in his latest book, The Rise of the Ultra Runners, published on Thursday (May 16). 

Over 12 years the number of races listed on a prominent ultra-running website has increased from 160 to 1,800, and smaller races have grown at a similar rate, writes Finn, who also details a huge rise in participation in the United States,  Britain and Asia.

The entry fee for the famous Marathon des Sables, a 156-mile desert race in Morocco that started back in the 1980s, is £4,250 – yet it is always sold out within minutes.

Ultra-running has no governing body, which leads to plenty of jostling for position, for status, and for money in what Finn calls "a Wild West of a sport".

None of this would impress Kouros, who has his own definition of what ultra-running is, and very clear ideas of what is acceptable, or ethical, and what is not.

Kouros says he is worried about those in the media and the sport who promote "fakers" as ultra-runners.

He believes hundreds, and maybe thousands of genuine ultra-runners have achieved far more than the "fakers" and says, "This unfairness has been established by liars who promote themselves with fake and unofficial activities reproduced by some journalists, companies and naive 'runners' who do not know what is ultra-running."

He is disdainful of solo runs, of trail races that cannot be measured accurately, and of any event or achievement that smacks of gimmickry.

Kouros places a strong emphasis on the mental or "spiritual" ability of competitors.

He acknowledges that ultra-running is not for the masses  but is worried that "fun-runners" - for example people who "collect" 100 marathons  - are taken too seriously.

"What counts is actual performances, not collections," Kouros says.

He has little respect for those who take part in events "with extreme terrain or temperatures, just to show off that they are tough".

A genuine ultra race, as far as Kouros is concerned, is competitive and continuous, and should last more than 24 hours.

He believes that races shorter than 100 miles are glorified marathons that do not test a runner’s "metaphysical characteristics".

Ultra-runners should have mental endurance that goes far beyond that of lesser athletes, should not keep taking breaks or rests, and should prove their "spiritual abilities" during a race.

His view is that "the verb endure is not a physical verb, it’s a spiritual one".

The man who finished third in that 1989 Westfield race, Kevin Mansell, says Kouros "had the mind and the athletic ability" that put him on a different level to everybody else.

Mansell competed against Kouros four times and his best performance was being beaten by "only" 21 hours.

"We were going out to get a good time, while he was going out for world records every time," said Mansell, one of the few men to have run Sydney-Melbourne inside six days.

"Yiannis Kouros is the greatest there ever was - a freak."