The first woman to officially run the Boston Marathon has marked five decades since her achievement by running it again – at the age of 70.

Kathrine Switzer completed the race under the qualifying time in 4 hours 44 minutes 31 seconds.

She made sporting history by completing the 1967 marathon despite being attacked by the race director at the time for being a woman.

Ms Switzer’s determination to finish the race won her plaudits and paved the way to equality for women in running.

Despite campaigning extensively for female participation in the sport, Ms Switzer has not run a marathon since 2011.

For the 121st Boston Marathon, race organisers have retired bib 261, in honour of the number Ms Switzer wore during the race in 1967. The Boston Marathon has only retired one other number in its history: 61, for 61 races begun by athlete Johnny Kelly.

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Ms Switzer – who has been running since she was 12 years old – decided to enter the race aged 20 after encouragement from her coach. Before entering, she had to prove to him she was capable of completing the race’s 26 miles.

“There were no real rules in 1967 stating that the Marathon was for men only,” Ms Switzer said.

“Nor was there anything indicating gender on the entry form. But almost all sports were for men. Women rarely participated. Most people assumed that women could not run the marathon distance and if they tried they would hurt themselves.”

Signing up using her initials KV Switzer – which didn’t identify her as female – she was allocated the number 261 for the marathon.

Because of the cold weather on the morning of the race, Ms Switzer and the rest of the runners stayed dressed in their warm up tracksuits, which she believes helped her blend in unnoticed by race organisers.

But she wasn’t hiding: “I was very proud of being a woman. I had long hair, wore lipstick and eyeliner to the start line. All the men around me knew that I was a woman.”

Two miles into the marathon, Ms Switzer was attacked by a race official.

“I jerked my head around quickly and looked square into the most vicious face I'd ever seen,” she recalled in her memoir.

“A big man, a huge man, with bared teeth was set to pounce, and before I could react he grabbed my shoulder and flung me back, screaming, 'Get the hell out of my race and give me those numbers!'”

Her boyfriend, who was running with her, managed to shove the official out of the way and Ms Switzer kept running.

“I knew if I dropped out no one would believe women could run distances and deserved to be in the Boston Marathon. They would just think that I was a clown, and that women were barging into events where they had no ability.

In pictures: Boston Marathon bombing anniversary Show all 15 1 /15 In pictures: Boston Marathon bombing anniversary In pictures: Boston Marathon bombing anniversary Boston, USA Boston Marathon bombing survivors, family members and supporters joined the relay runners for the final half-block to the finish In pictures: Boston Marathon bombing anniversary Boston, USA Boston Marathon bombing survivors Doug Julian (L) and his partner Lynn Crisci (C) hug as fellow survivor Shannon Silvestri (R) looks on in Boston. The trio, joined by other survivors, family members and supporters met up with participants of a cross country charity relay that began in California and ended at the finish line of the Boston Marathon In pictures: Boston Marathon bombing anniversary Boston, USA Rosa Evora (C) hugs a fellow participant in a cross country relay that began in California and ended at the Boston Marathon finish line in Boston In pictures: Boston Marathon bombing anniversary Boston, USA Supporters of slain MIT police officer Sean Collier carry a banner to the finish line of the Boston Marathon In pictures: Boston Marathon bombing anniversary Boston, USA Boston Marathon bombing survivor Heather Abbott carries a symbolic torch as she crosses the marathon finish line in Boston In pictures: Boston Marathon bombing anniversary Boston, USA People walk past an electronic billboard reading "Boston Strong" near the finish line of the Boston Marathon In pictures: Boston Marathon bombing anniversary Boston, USA Crosses bearing the names of people killed are displayed in an exhibit titled, "Dear Boston: Messages from the Marathon Memorial" in the Boston Public Library to commemorate the 2013 Boston Maraton bombings In pictures: Boston Marathon bombing anniversary Boston, USA Pedestrians look at a marathon banner installation at the Old South Church on Boylston Street in Boston In pictures: Boston Marathon bombing anniversary Boston, USA Visitors stand next to the Runner's shoes display titled, "Dear Boston: Messages from the Marathon Memorial" in the Boston Public Library to commemorate the 2013 Boston Maraton bombings In pictures: Boston Marathon bombing anniversary Boston, USA Runner's shoes are laid out in a display titled, "Dear Boston: Messages from the Marathon Memorial" in the Boston Public Library to commemorate the 2013 Boston Maraton bombings In pictures: Boston Marathon bombing anniversary Boston, USA A runner's shoes read, "I will run the Boston Marathong for you," in a display titled, "Dear Boston: Messages from the Marathon Memorial" in the Boston Public Library to commemorate the 2013 Boston Maraton bombings In pictures: Boston Marathon bombing anniversary Boston, USA Jillian Munson, from Rochester, New York, hangs a hand-written message she wrote on a tree hung with messages inside a display titled, "Dear Boston: Messages from the Marathon Memorial" in the Boston Public Library to commemorate the 2013 Boston Maraton bombings In pictures: Boston Marathon bombing anniversary Boston, USA Hand written messages are displayed in an exhibit titled, "Dear Boston: Messages from the Marathon Memorial" in the Boston Public Library to commemorate the 2013 Boston Maraton bombings In pictures: Boston Marathon bombing anniversary Boston, USA A passer-by walks past yellow and blue crocheted hearts that hang from a lamp post in front of the Forum restaurant near the finish line of the Boston Marathon. The restaurant was damaged after one of the bombs exploded in front of the building during the race In pictures: Boston Marathon bombing anniversary Boston, USA Police officers patrol the finish line of the Boston Marathon

“I was serious about my running and I could not let fear stop me.”

Ms Switzer went on to campaign for women’s running and was pivotal in gaining the introduction of the women’s marathon to the 1984 Olympic games. She now runs a campaign named 261 Fearless, which encourages women to run.