The actor: Prasanna Puwanarajah

A few years ago, Prasanna Puwanarajah was about to step out on stage with the Royal Shakespeare Company when a member of the audience fainted. Puwanarajah, who trained as a surgeon before embarking on a second career as an actor, director and playwright, was called out from backstage to help. “I was playing the priest in Twelfth Night,” he says. “I was in full Greek Orthodox costume. I came out into the foyer, and the lady who had fainted took one look at me and said, ‘It’s a very good service here, isn’t it?’”

The fact that Puwanarajah became an actor at all is, he says, largely down to happenstance. Growing up in Hampshire, he was more interested in science and sport than theatre. He enjoyed school plays and did a season with the National Youth Theatre aged 17, but remained set on going to medical school. “Acting was just not in the serious part of my head,” he says over coffee at the National Theatre, the place he considers central to his career change. “I loved it and it was fun, but that’s all it was to me.”

He studied medicine at Oxford, where he continued acting and directing. But theatre remained no more than a hobby until, after several years of working as a junior doctor, Puwanarajah decided to take a year out and give acting a go. As the acting began to gather momentum, he deferred his medical training for another year, finally deciding to leave medicine for good when the National offered him an audition. “That was the moment everything changed,” he says. “Until then, I was really just a doctor doing a bit of acting.”

At 33, Puwanarajah has come to his second career early enough to have a decent stab at making it big. Acting and writing are more forgiving of late starts than other art forms: many big-name actors and dramatists, from Alan Rickman to Dennis Kelly, had other careers first. And Puwanarajah believes his medical background actually complements his acting. “I love medicine,” he says. “I never saw it as just a safety net. And there’s actually a lot of common ground. Interrogating a set of circumstances is the work of any rehearsal room. It’s also the work of any clinical situation.”

Puwanarajah’s career change appears to be paying off: he’s worked with several major companies and is performing in a new production, Dara, at the National this month. Also, rather brilliantly, he plays a doctor in the new Sky1 medical drama Critical. His writing is going well, too. The National produced his debut play, Nightwatchman, in 2011, and he is working on a new piece with actor Riz Ahmed and playwright DC Moore.

His medical expertise still comes in handy, though, and not only for resuscitating audience members. While rehearsing the National’s 2013 production of Othello, Puwanarajah briefed Olivia Vinall, playing Desdemona, on the physiological effects of strangling. What would he do if someone became seriously ill while he was actually acting on stage? “I’d probably go and help them,” he says after a moment’s hesitation. “It’s only a play, after all.”

The poet: Sheila Hillier

Sheila Hillier fell in love with poetry as a child: her mother would read poems aloud and, inspired, Hillier began to write reams of her own. But at 15, she decided to give up writing and concentrate on science. “I felt a sort of vocation,” she says. “And I suppose I saw writing as a kind of self-indulgence. It was rather frightening.” She laughs. “If I allowed myself to go down that path, I thought, where would it all end?”

The path Hillier took led her to a successful career as a medical sociologist: she is an emeritus professor at Barts and the London School of Medicine and Dentistry, and has spent her life studying the spread of infectious disease. But she never let go of that early passion for poetry – and now, at 70, Hillier has finally found a new career as a poet.

We meet in Hillier’s stylish, book-lined flat in London’s Barbican; her daughter Martha, a screenwriter, lives in one of the adjacent towers. It was Martha who inspired Hillier to return to writing after a four-decade gap. In 2001, she suggested her mother take a writing course at City Lit, an adult-education college. It proved a turning point. “The teacher asked if I’d ever thought about writing poetry,” Hillier says. “With that, she changed my life.”

Hillier began writing seriously again, and enrolled in a distance-learning MA. A few years later, she won the Poetry Society’s prestigious Hamish Canham prize; she has now published two volumes of verse and is working on a novel. She writes every day now, keeping office hours, and the pleasure she takes in her new routine is palpable. “Being able to express yourself in words is just an incredible thing,” she says. “Through all the years I wasn’t writing, I still kept notebooks filled with ideas. But I didn’t read any contemporary poetry at all: I just thought it would upset me.”

Taking up writing later in life has its challenges: she is, she says, less interested in networking than most young writers, and is frank about the loss of status incurred by taking up a new art form more or less from scratch. “You have to be humble,” she says. “You may be 60-plus years old, but actually [in this new field], you’re 20.”

What would she say to anyone considering making a similar life-change? “Do it. I don’t regret anything about the life I have had. But if I hadn’t started writing when I did, I honestly think I would be dead by now.”

The choreographer: Mari Frogner

One day six years ago, Mari Frogner was walking down the street when she experienced a strange physical sensation. “It felt,” she says, “as if I had grown arms and wings – as if, suddenly, I had all the limbs I was supposed to have.”

Six months before, Frogner had quit her job as an economic adviser to the Department for Work and Pensions to retrain as a dancer. She now believes that this decision lay behind that strange sensation in the street. “In the office,” she says, “I had felt so physically restrained. It felt right to be dancing. It was as if my body now felt free.”

Frogner was 33 and had just embarked on a postgraduate diploma in professional dance at the Trinity Laban conservatoire in London. Now on the cusp of 40, she has left economics behind, establishing herself as a choreographer to watch with her own dance company, Nutshell. Frogner studied ballet as a child in Bergen, Norway, but turned down a place at dance school. “I had some knee trouble,” she says, “and I was very tall for a dancer. With hindsight, I think I could have had a career, but at the time I just didn’t dare.”

A degree in economics followed, then a career in the same field. But when she hit 30, she rediscovered her love of dance, and began slipping off to ballet classes on her lunchbreak. She was clear about her limitations, however. “I wasn’t nearly as flexible as I used to be. I didn’t have any balance, and my feet didn’t point. But there was a muscle memory there.”

With the support of her husband Neil, Frogner gradually resolved to retrain as a choreographer. Money wasn’t too much of an issue – they’d both saved hard – and by opting for choreography, Frogner’s age and relative lack of experience wouldn’t matter as they would had she been set on becoming a prima ballerina (such a step, it seems safe to assume, would have been unprecedented – an amateur performer in her 30s becoming a professional ballet star). At Trinity Laban, Frogner felt immediately at home. “There was a massive cross-section of people on the course, from 18 to 50. I never felt old.”

The only frustration of coming to dance later in life lies, Frogner says, in the difficulty of securing funding. Most opportunities for emerging artists have an upper age limit of 25 or 30, making Frogner ineligible. “It has been a challenge,” she admits, “but it’s just forced me to be more ambitious.”

That ambition seems to be paying dividends: she’s created several works in the last few years. Her latest, Physical Science, is opening at London’s Blue Elephant theatre next month. “The dream, when I left my job, was just to give dance a go,” she says. “If nothing came of it, I could always take another job as an economist. The fact that this has worked out is beyond anything I imagined.”

The pianist: Gil Jetley

One day in 1967, Gil Jetley’s early journey towards becoming a professional pianist ended abruptly. He was 18 and living in a hostel while studying piano and composition at London’s Royal Academy of Music. But he wasn’t enjoying it and couldn’t imagine being able to make a living as a musician. So, while passing the nearby offices of IBM one day, he went in and just asked for a job. “They offered me one – and I took it. I just didn’t have the confidence to carry on with music.”

It hadn’t helped that Jetley, who’s from Worthing in West Sussex, had grown up in a family of non-musicians who expected him to get a conventional job. “I’d practise the piano for two or three hours,” he says, “and my mother would ask, ‘When are you going to get off your backside and do some real work?’” And that’s what Jetley did: for the next four decades, he worked in IT and teaching, moving first to Singapore then to New Zealand.

He still played the piano in his spare time, but it wasn’t until he took a job managing the Nelson School of Music on New Zealand’s South Island that music re-entered Jetley’s life in a serious way. When the Russian pianist Konstantin Scherbakov performed at the school in 1995, Jetley suddenly realised what he’d been missing. “His playing was a revelation,” he says. “The sound he made was different, the whole atmosphere he created was an inspiration. I just wanted to play again.”

Jetley is now back in England, finally setting out his stall as a concert pianist. He’s keeping his expectations realistic: he doesn’t dream of filling the Festival Hall, or reaching Scherbakov’s giddy heights. Instead, he sees himself as operating somewhere in the busy hinterland between amateur and professional, and has won several awards for players in that bracket – including, in 2013, Guardian editor Alan Rusbridger’s Chopin competition, Play It Again. Jetley also gives regular recitals, practising on an electric piano in the small spare bedroom of his home in Beckenham, south London.

He knows he has missed out on years of playing and enjoying music, not to mention the professional career that might have been his had he not walked into the IBM building all those years ago. “I don’t know if other creative people feel the same way,” he says, “but usually the reason you’re not being creative any more is because you’re so involved with your other work. You don’t really miss it, but you know you’re not happy, not satisfied – and it’s difficult to work out why. It was only relatively lately that I realised there was a big gap in my life.”

At 65, Jetley has finally filled that gap, and he doesn’t believe his age poses any obstacle to pursuing his passion. “At most of the competitions I enter,” he says, “nobody is younger than 30. They’ve all missed the boat in terms of being professional, though the oldest is often older than me by quite a few years. It’s a bit late for me – but not too late.”