When best-selling author Adam Kay rushed into the hospital where his premature baby had just been born, it brought back all the highs and lows of working as a junior doctor.

“Every bleep’s a reminder of another emergency, every alarm makes you jump to your feet. It definitely brought back a lot of memories,” says the writer and comedian, whose best-selling 2017 book This Is Going To Hurt charted his time as a junior doctor in obstetrics and gynaecology and was made into an award-winning TV series starring Ben Whishaw. The pair still keep in touch.

Kay, 44, who is married to TV producer James Farrell, never imagined that he’d have to watch his baby being born by emergency caesarean on FaceTime, but it was a long-distance birth via surrogate in Washington DC and the baby came five weeks early. He and Farrell were at the theatre in London when they got the call.

“We’d sorted our flights for a week later. We got the call in the theatre, James ran out and she told him her waters had broken. It was like a film, ‘Right, Heathrow Airport!’”

They only managed to secure one-flight ticket at such short notice, so Farrell went.

“He got to the hospital with 15 minutes to spare before the emergency caesarean was carried out, so I watched it on FaceTime and got the next flight out in the morning,” recalls Kay, whose daughter Ruby is now 22-months-old, while her brother Ziggy, also born via a surrogate, is four months younger.

“I felt guilt for not being there, then excitement because, ‘Oh my God, this is our baby being born!’ and then terror when it was quite clear that there were all these paediatricians around and tubes and wires. It was hugely stressful and brought back all the memories (of his time as a junior doctor).

“Ruby was under two kilos when she was born, very tiny,” says Kay, who is continuing his UK tour of Undoctored based on his subsequent 2022 memoir, which follows his path to comedy and writing after leaving medicine.

“She was a little scrap – she was in neonatal intensive care and was definitely a fighter, and since she’s been out she’s never stopped fighting. She’s just so loud and big and we’ve got every parent’s fear that she may want to be an actor.”

The couple had thought long and hard about having children, he agrees.

“For me, one of the biggest blocks was a slightly psychological thing about not really wanting to go back on to a labour ward again. It was very strange being back in that environment – and slightly traumatic.”

He certainly wasn’t going to miss Ziggy’s birth – and they were there months before the due date, he chuckles. He wasn’t involved in the delivery.

“No, leave that to the professionals. But it’s very weird being on the other side of the counter, sitting on your hands, trusting expert professionals to do their job.”

Kay left medicine in 2010 after a caesarean section went horribly wrong on a shift when he was the most senior person on the ward. The patient had an undiagnosed placenta praevia, the baby died and the mother lost 12 litres of blood and ended up having a hysterectomy – it was hugely traumatic.

“I left after a difficult time on the wards and I think a lot of the trauma of that was slightly unresolved, even though it was a long time ago,” he reflects.

He still has counselling and is in a much better place mentally than he was a decade ago, he says, thanks to being able to open up to his husband, friends and family, as well as receiving professional support.

This Is Going To Hurt, published in 2017, has sold more than three million copies and was followed by several more anecdotal reads based on his experiences and numerous children’s titles. He has now written the first in a new children’s fiction medical mystery series, Dexter Procter The 10-Year-Old Doctor.

The eponymous hero is a genius-from-birth kid, who started speaking at four seconds old, had 87 A-levels by the age of three and by 10 is working as a paediatrician at a hospital. It’s a light-hearted yarn tempered with easy-to-process information for children about what may happen when you are in hospital.

“I wanted it to be funny, silly, still a bit disgusting. I liked the idea of demystifying hospitals and doctors and medicine a bit for kids because hospitals are scary places.”

Fatherhood, he says, has completely refocused his perspective.

“All the stuff that used to stress me out no longer stresses me out because it’s all about the kids. You realise how selfish you’ve been beforehand. Your priorities were around yourself predominantly.”

It’s also given him much more material, he agrees, and confesses that his diaries in which he scribbles thoughts are pretty full, although he’s not planning any shows based on fatherhood imminently.

“I write stuff down to help me process everything, but I’m really excited about my kids getting to an age when I can force my books on them (he has written numerous children’s books),” he adds.

He and his family live in Oxfordshire and currently Kay writes largely at night, which is compatible with looking after babies, as he strives to maintain his work-life balance. He’s currently writing the sequel to Dexter Procter.

“I used to write seven days a week. Now I make sure we have proper weekends. I love my work, but I increasingly love my home life.”

As well as his writing – his debut novel, A Particularly Nasty Case, will be out next September –  and performing, he will be supporting charities including MediCinema and Starlight  at various children’s hospital events in the autumn.

Kay is clearly a deeply caring individual, and behind the hilarious and heartbreaking anecdotes about life as a junior doctor there’s a simmering anger.

He talks of the NHS being  “broken”, the lack of mental health provision, of the exodus of NHS staff because of how they are treated, and was fully behind the junior doctors’ strikes. He does what he can on his celebrity platform to highlight the issues which trouble him.

He says he wouldn’t want to go into politics, adding: “I think I’m a good troublemaker. I’d like to maintain my position as a troublemaker annoying politicians or helping in any way if I can if they’re interested in my thoughts.”

He’s much more hopeful about the NHS with a Labour government.

“I’ve met (Health Secretary) Wes Streeting at an NHS charity awards event and he seems like a nice man. I’ve been impressed by some of the stuff he’s said and sceptical about other stuff he’s said. But this is all words. The NHS needs big action.”

He would worry, he says, if either of his children decided to go into medicine.

“It’s a very tough job in all ways, from the hours to the emotional toll it takes, and who knows what the NHS will be like when they are doing their GCSEs in 14 years? Who knows if there will even be an NHS in 14 years?”

Despite all this, he increasingly misses being a doctor.

“Maybe some of the bad stuff’s faded in my mind or maybe the NHS is getting worse and I feel for the people who are working there and I feel increasingly sorry for leaving them in the lurch and being another name on the list of doctors who’ve left.

“But I’ve got some ideas about how I can get involved with the education and policy side and just try to give something back.”

Dexter Procter The 10-Year-Old Doctor by Adam Kay is published by Puffin on September 12, priced £14.99.