The Soviet Union were joined by three Warsaw Pact countries - Poland, Bulgaria and Hungary - in an attack led by 250,000 combined troops, a number later increased to about 500,000, supported by thousands of tanks and hundreds of aircraft.

It was code-named "Operation Danube" and was designed to crush the Prague Spring, a reform era started under new Czechoslovakian leader Alexander Dubcek, who shook up the political establishment by implementing freedom of the press, freedom of speech and freedom of travel, along with economic reforms. These liberalisation efforts, which he called "socialism with a human face," won popular support from his citizens.

Even as the Soviet tanks rumbled through the Czech capital, backing for Dubcek’s reforms came from all levels of society, including the most famous Czech of the time. Emil Zatopek, who at Helsinki in 1952 had become the first runner in history to win the 5,000 metres, 10,000m and marathon at the same Olympics, had been among those that had stood on the front line with his wife Dana to show their support for the fight for greater freedom and improved living standards.

Emil and Dana, herself an Olympic gold medallist, signed the "Two Thousands Words," a statement of defiance, of unity against the colossus to the East, signed by many prominent people. As Moscow re-asserted its iron grip on Czechoslovakia and drew it back into its orbit, there was no problem finding the dissidents. Their names were on the manifesto.

In 1996, I was fortunate enough to sit down with Zatopek for more than two hours at the International Association of Athletics Federations World Marathon Cup in Athens where the great and good had been invited to celebrate the centenary of the first Olympic marathon. It was the most interesting interview of my career.

"I went to Wenceslaus Square to talk to the Russians," Zatopek told me over a glass of red wine as he recalled those events in 1968. "They did not want to listen, but the people kept saying: 'Hear him out. Do you know your Olympic champions? He is our Olympic champion.' Finally, an officer came over. I told him that this invasion was one-sided, that it was offensive to all of us, that it only hurt the Communist movement."

The Soviets did not listen and retribution against the dissidents was swift and brutal. Doctors became window cleaners. Scientists became truck drivers. Legends became navvies. No one could complain. No one could talk. "The Russians came like barbarians," Zatopek said. "They had their tanks, their cannons. We are not guilty of anything, but what are we going to do? We cannot charge tanks. It was like the end. No chance."

Zatopek was dropped from the army and expelled from the Communist Party. He could not find work in Prague. "I kept looking and looking, but no one would hire me," he said. "I could not understand. Finally, a man told me that everyone in Prague was afraid to hire me. He said I would have to find work outside the city."

The greatest distance runner of all time became a member of a geological survey team, which searched for minerals in the back lands of the country. The job was digging, doing construction. He dug. He lifted sacks of cement. He left home and lived in a trailer for stretches of 10 and 14 days. The work began at seven in the morning and ended at eight at night. When he came home for a fortnight, he was exhausted. It left him with the legacy of an irregular heartbeat. "It was working down the uranium mines," he said.

With the end of the Cold War, the Czech Defence Minister issued a public apology to Zatopek, and he was feted by the new President, Vaclav Havel. He was given a pension by the Government but survived thanks to a stipend from Adidas, for whom he filmed commercials.

I thought of Zatopek, who died in September 2000, as Russia invaded Ukraine. He was born 100 years ago this September and a special campaign had been organised back in his homeland to celebrate this and the 70th anniversary of his amazing achievement at Helsinki 1952.

But, even in death, the Russians will not leave Zatopek alone. RunCzech had to announce last week it has been forced to amend the promotional campaign to commemorate Zátopek due to use of the letter "Z," which has become used as a symbol of Russia in their war in Ukraine.

"The advertising campaign was created by leading creatives and counted on the gradual discovery of the entire message from the unfortunate letter Z to visuals with a running legend and messages like 'This season is all about Z' or 'RunCzech remember,’” RunCzech President Carlo Capalbo said.

"Even though it is just a letter of the alphabet, which is supposed to remind a Czech phenomenal athlete, we do not want it to be associated with aggression and evoke unpleasant emotions."

At that World Marathon Cup in Athens more than a quarter-of-a-century ago, the status that Zatopek was held in by everybody was clear.

Between them, Sohn Kee-Chung, Waldemar Cierpinski, Carlos Lopes, Gelindo Bordin, Hwang Young-cho, Rosa Mota and Valentina Yegorova could have claimed to have won eight Olympic marathon gold medals. But, on this day at a hotel restaurant in Athens, they had formed an orderly queue at the table of Zatopek to offer him their menu cards to sign. They shuffled forward patiently, clearly excited at meeting such a famous celebrity.

Kee-Chung, revered as a hero in his own country for the way he defied the Japanese occupiers by insisting that he was a Korean and nothing else after his Olympic victory in Berlin in 1936, bowed as he approached the table as if greeting royalty. Bordin, the Italian who won in Seoul in 1988 and spurred a national jogging boom, said: "Many say that I am a great runner because I won a gold medal. So, what does this make this man?"

To me, Zatopek remains the greatest distance runner of all time. He set 18 world records and had a six-year run of 38 victories in the 10,000m. As well as his three Olympic gold medals at Helsinki 1952, he also won the 10,000m at London 1948 and a silver in the 5,000m.

Yet merely to list Zatopek’s athletic accomplishments misses the man. On that warm spring evening in the Greek capital, the cradle of the Olympic Movement, he fairly burst with enthusiasm for life, greeting strangers with openness, sitting around a table conversing in a variety of languages or spontaneously breaking into song. Zatopek’s honesty, charm and humility, plus his courage in the face of Soviet repression, had made him a genuine hero.

On this special occasion, Zatopek did not see himself as a legend but as an athlete meeting kindred spirits. He was clearly thrilled to see people he had watched only on the television at his modest bungalow in Prague. "So, you are the great Lopes," he said as the 1984 Olympic champion from Portugal introduced himself. "I must have your autograph. Wait till I tell Dana I have met you. She will be very jealous. She is a big fan."

Part of the Zatopek legend stemmed from his unforgettable running style. It was once described as "the most frightful horror spectacle since Frankenstein." Where other runners were graceful, like human gazelles, the Czech runner "seemed on the verge of strangulation; his hatchet face was crimson; his tongue lolled out."

Hard work was his ally. He ran miles and miles and more miles, often more than 100 a week. He trained in hard combat boots to make his feet feel lighter on race day. He ran the stairs of stadiums for endurance. He ran in place in his bath.

"I started late," he said. "I was almost 19. I never had participated in any organised sports. I was working in a shoe factory in Zlin, where I was born. The director of the factory said one day that there would be a race through the city on Sunday, and that I should run. I did not want to go. I told him I had a cold. I told him I had a bad knee. He made me go to the company doctor. The doctor said I was fine. I had to run. I surprised myself. I finished second."

The sport was his release. He ran through World War Two. The Nazis had taken over his country so quickly in 1939 that it hardly had a chance to whimper. He ran through the Nazi era. The austerity of his situation somehow helped him become a better runner.

"If there is luxury, there is the danger of degeneration," he said. "Sit behind the wheel of a car and a man gains time but loses condition. There was no car. I ran instead. Look at the distance champions today. They are mostly Africans. Runners from underdeveloped countries. They are not softened by luxury."

When the War ended, he was drafted into the new Czech army and at first thought it was a terrible fate. Terrible? The army wanted him to run. He ran in the best facilities with the best trainers. He was soon breaking national records.

As the 1948 Olympics in London approached, he was Czechoslovakia’s best hope. A few weeks before the Games he attended a meeting at which his chances of breaking the national record for 3,000m became the focus of attention.

"I was warming up when there was a great roar and the announcement that a record had been set. I said, 'What is this? A record? How can it be? I have not run yet.' I was told it was a record in the women’s javelin. I was asked to congratulate the woman. I did. We had our pictures taken together. Then I set my record, and she congratulated me."

It was Dana. He was strumming songs for her on the guitar by the time they went to London. He won the 10,000m, the first runner to win an Olympic gold for Czechoslovakia. He finished second in the 5,000m. She finished seventh in the javelin. They married two months later. Their apartment in Prague became part home, part gymnasium. Each had a separate training schedule, but at night they would throw a medicine ball to each other. Sometimes the ball landed on the floor, and the neighbours downstairs would complain. They would go for picnics in the woods on weekends. She would prepare the lunch. He would plan the direction of the training run.

"Dana used to complain that we never had normal picnics," Emil laughed. "So, I promised her we could and then I would go off on a 25km run."

At the Helsinki Olympics, the local story became the Worlds. Emil noticed that the schedule offered the possibility of running the 10,000m, the 5,000m and the marathon. There were two days of rest between the first two events, then three before the marathon. He would try all three. Dana noticed something else: the 5,000m final would be run at the same time as the women’s javelin final.

But she still had not performed when the 5,000m was run. She was waiting in the tunnel leading into the stadium. All she could hear was noise followed by silence. Who had won? It was Emil. By the time the medal was awarded, and the Czech anthem was played, she had come into the stadium. She was able to yell to her husband as he took a victory lap.

"Emil," Dana said. "Give me the medal. I will put it in my bag for luck."

She carried the bag, as well as her emotions, to the competition. On the first of her throws, she propelled the javelin far enough to win the gold medal in a stunning upset. Emil had already won the 10,000m and he finished the Olympics by winning the marathon. It was the first marathon he ever had run. He had never raced so far before and chose to follow the favourite, Jim Peters of Britain. He had never met Peters but knew his race number and said to him at the start: "Hello, I am Zatopek."

Peters led for 15 kilometres when Zatopek pulled up to him and wondered aloud: "The pace is it too fast?” Peters responded: “It is too slow." After that, Zatopek took the lead. He won by two-and-a-half minutes. Emil and Dana returned home as heroes.

The next day after our interview in Athens I saw Zatopek at the airport and approached him to say goodbye. He kissed me on both cheeks and thanked me for remembering him. I told him that as long as people ran, he would be remembered.

"Do you really think so?" he said.

Emil Zatopek: a true champion, on and off the track. A great man and a humble person.