It was the moment when she thought that her boyfriend had killed the race director, the incident that gave life to women’s marathon running. Kathrine Switzer remembers it as clearly today as the afternoon it happened in 1967. An enraged former Scottish shipyard worker tried to remove Switzer from an all-male marathon after she had tricked her way into the race.

It was an act of audacity for which the expected 12,000 women running in the Flora London Marathon on Sunday, and women marathon runners everywhere, should be grateful. But, in a week that marks the 40th anniversary of Switzer’s historic first step towards women’s equality in distance running, there was a reminder yesterday that it is a battle still to be won.

The manhandling of Switzer in front of the press truck during the 1967 Boston Marathon and the international publicity generated by a photograph of the scuffle gave her the platform to lead the campaign for the women’s marathon to be added to the Olympic programme in 1984. But not before she had persuaded Boston, the world’s oldest annual marathon, that began in 1897, to admit women from 1972.

By entering Boston as K. V. Switzer, the New York student of journalism was accepted on the presumption of being a man. All went to plan until four miles into the race, when Switzer’s presence was angrily challenged by Jock Semple, the race director, who was, by Switzer’s recollection, “a real tough case from a hard background”.

A Glaswegian who had emigrated to the United States, Semple was travelling on the press truck when he was alerted to a woman wearing an official number. Another woman, Roberta Gibb, had run the year before and was running again, but without a number. Switzer, though, had gone too far.

Semple jumped off the truck and accosted Switzer from behind, shouting: “Get the hell out of my race and give me that number.” What he had not bargained for was Switzer’s boyfriend, Tom Miller, a 16st hammer thrower, running alongside.

Recalling the incident for The Times, Switzer said: “Tom was out of control. When he hit Jock, he hit him hard and sent him flying and he landed on the side of the road. I thought, ‘My God, you’ve killed him.’ ” Her concern was short-lived, until the truck caught up with Semple hanging off the side. “I was so relieved to see him alive,” Switzer said.

Had Semple not picked a fight with Switzer, there would have been no autobiography, which has been published to coincide with the anniversary.

“If Jock had tackled Roberta Gibb in 1966 in front of the press truck, it would perhaps have been a different story,” Semple said. “I would not have had the vehicle [to campaign] without that incredible photograph.”

Women had given the lie to the argument that they were too frail for the marathon — the world record at the time was 3hr 19min — but stubbornness prevailed. Switzer, however, gradually wore down Semple’s resistance and, after Boston accepted women, the two became friends.

“When Jock saw me wearing numbers, he assumed I was a clown making a mockery of his race, but years later he realised that I loved Boston as much as he did,” Switzer said.

In 1980, Switzer helped to put on the Avon international women’s marathon in London, to the concern of Chris Brasher, the founder of the London Marathon as we know it today. The book repeats a combative exchange between Switzer and Brasher as he tries to persuade her to take her race to Edinburgh, apparently worried at the threat to his project.

Switzer had planned to take the Avon Marathon to other cities, however, and Brasher’s baby is 26 years old this weekend. Appropriately, Lornah Kiplagat, a pioneer in the Switzer mould, is favourite to take the women’s title. A Kenyan-born Dutchwoman, Kiplagat funds a training camp in Iten, western Kenya, for women athletes.

Switzer’s job may be done, but Kiplagat has stronger prejudices to overcome. “In Kenya, women think it is normal to do everything for men,” she said yesterday. “This is why there are so many Kenyan men in international running and so few women. For women, there is not the support.”

It was Switzer’s 1980 Avon Marathon in London that, she said, was the “deal-maker” in getting the women’s marathon into the Olympics. London was the home of the IAAF and the number of countries taking part met IOC requirements. Now, 23 years on, more women are registered runners in races in the US than men. Kenya has some catching up to do.