At 85-years-old, this retired concert pianist who only began running in later life can complete a half marathon in just over two hours.
At 85-years-old, this retired concert pianist who only began running in later life can complete a half marathon in just over two hours and holds the world record time for her age.
"Before I turned 78, the last time I ran was in college, and I was really bad," she said, standing in her home in front of a wall of some 500 medals recognising her athletic feats.
Stopping for selfies with children and to offer her fellow runners encouragement, Larkin has become a major draw at the races she runs.
"As people pass me, because most people pass me, they greet me and say 'hello -- I saw you on TV!' Otherwise we don't really talk for any length of time because you need your breath," she said following a recent 10-km race in Pretoria.
Her late fame as a runner has come as a surprise for the pianist who arrived in South Africa from Britain in 1970.
Shortly after 2000, Larkin's doctor diagnosed her with osteoporosis which she was unable to treat with medication or injections.
Then in 2010, one of her four children briefly moved into her home in Johannesburg's middle-class Randburg suburb -- where she has been dubbed by local media the "Grand Dame of Randburg".
"My son ran three times a week. I said I would join him. When I started, I was walking three steps, running three steps, walking three steps...," she recalled.
Just seven years later, her running had been transformed. In May she was invited to compete in Switzerland where she completed a half-marathon in two hours five minutes, setting a world record for her age group.
"Running in Geneva was absolute magic, the race itself was lovely. It was flat, you started in the gardens, you came to the fields and you ran alongside the lake," she said.
To stay in shape, Larkin adheres to a strict regimen -- no sugar, salt or coffee and a 5:00 am start every day for training.
Last year alone she ran in 65 races, including several 21 kilometre (13 mile) half-marathons.
"There's always an element of disbelief. I can't believe I've done it. But my body tells me the next day I certainly did it," she said.
"My blood goes around my body much quicker, I don't feel cold, I can feel all the muscles in my body -- I never knew I've got so many muscles! I feel much more alive."
Once her gruelling morning routine is complete, Larkin doesn't take time to rest. Jumping into her small yellow car she heads to a private college in the north of the city to give piano lessons.
Still stressed in her pink and blue Nike running shoes, but having swapped her shorts for trousers, Larkin put a teenage girl through her paces while wielding a conductor's baton.
The former concert pianist does not allow a single error to go unmentioned -- but still congratulates the pupil on her progress.
"After lessons I'm usually very exhausted... (but) it reminds me that I can do whatever I want to do because she's defying all odds," said the 17-year-old student Vuyo Tshwele as she paused between scales.
Every week some 30 students gather to learn from Larkin's experience, formed over many years of playing in Vienna and Britain, as well as South Africa.
And despite preparing to turn 86 in September, Larkin has no intention of slowing down.
"I can imagine a life without running but it's a kind of slow death," she said. "I'm going to run as long as I can -- even if I only have one leg, I'll manage."