When ex-junior doctor and comedian Adam Kay, bestselling author of This Is Going To Hurt, set out to raise money for NHS charities through a compilation of NHS-focused celebrity anecdotes, he never expected the avalanche of responses he would receive.
"I was amazed. I thought we wouldn't be so near the top of the barrel. It was a dream line-up. But when I started reading what the NHS means to all these people, I thought, we've all got a personal experience of the NHS and they're just the same as us. They've just got more Instagram followers."
Dear NHS: 100 Stories To Say Thank You, edited by Kay, crams in 109 contributions from famous faces (the title was chosen before all the responses came back) including Jo Brand and Dawn French, Sir Michael Palin, Sir Paul McCartney, Dame Julie Walters, Ed Sheeran and Martin Freeman. It opens with Graham Norton's revelation that he was stabbed by muggers as he walked home from a party when he was at drama school.
There's Stephen Fry's recollection of having his stomach pumped aged 17 after taking a cocktail of drugs, Sir Michael Palin's recovery from heart surgery last year, Emilia Clarke's brain haemorrhage trauma, Naomie Harris's spine operation...
There are stories from those who lost loved ones to cancer or other diseases in hospital. Some saw their relatives recover against the odds, others witnessed them slip away.
The common thread, however, is their unwavering thanks to the NHS, to the selfless, compassionate treatment by nurses, doctors and others who helped ease them through pain, trauma and loss, in whatever form. It is the love for the NHS and how it touches our lives that stands out.
Kay and his husband, TV producer James Farrell, contacted celebrity friends and agents to get the ball rolling, and the approaches to people like Jonathan Ross and Konnie Huq soon had a ripple effect, he recalls.
"I was surprised by people's responses. I didn't want to dictate what the book was. I didn't give them a steer. I thought Jimmy Carr would write something hilarious. He writes painfully and movingly about the death of his mum.
"I had no idea about all the health problems that Jacqueline Wilson has had; we all think we know Graham Norton and then he writes about such an enormous thing to have happened to him; Jamie Oliver's interpretation is, 'Let's make some food for the NHS workers'."
The Covid-19 crisis had made former junior doctor Kay, who quit the NHS in 2010, wish he could do something to help.
"Ever since I've left (the NHS) I've had this ongoing feeling of being less useful," he reflects.
"The thing you miss most when you leave the profession is when you're driving home three hours late covered in blood but you still have a smile on your face because you've been at work doing something useful."
The stories aren't just testimonials, but secrets and memories shared, comedies and tragedies of life which we all recognise, Kay notes.
He seems to have coped well in lockdown, despite the postponement of his tour dates and the delay of filming the eight-part BBC2 TV adaptation of This Is Going To Hurt, a memoir in diary form of his life as a doctor working in obstetrics and gynaecology. Ben Whishaw will play Kay, who has written the script, while Farrell is producing it.
"It's somewhere between comedy and drama. I'm so excited that Ben Whishaw is playing me. He's one of the greatest actors that we've ever produced. He was always at the top of our list."
But things could have been much worse than his work schedule being put on hold, he reflects.
"I'm one of the lucky ones. I've not lost any family or friends, which is the most important thing. I have a garden and I'm not putting my life at risk on the front line, so all things considered..."
Kay and Farrell moved from London to a little village in Oxfordshire at the end of last year, where they spent lockdown.
"Our friends thought it was some breakdown, but in retrospect it was quite prescient as it means we have a garden, which makes us extremely lucky. I've got lots of friends on floor 13 of a London high rise."
Two of his siblings are doctors and he admits he does worry about them, along with many of his friends who work on the front line.
"A friend of mine said on Facebook right at the start, when doctors and nurses and midwives were dying when there was a crisis with PPE, 'This isn't really what I signed up for' and it's true. You don't go to medical school thinking that, 'This might cost me my life'."
He's abided by the lockdown rules, wears a face mask wherever he goes and won't be hurrying to the pub any time soon, he says.
"My gut feeling is that we are being hasty in getting back to normal and all we are doing is hastening 'volume two' of the story. It isn't over. People are dying. It worries me."
But there is a lot of confusing information out there, he observes.
"My husband spends a lot of time on the internet reading studies or articles of dubious value," he says, wryly. "He gets very worried by this sort of stuff. He'll read something that says, 'The virus can persist on packets of (cereal) for a fortnight' and suddenly we are Dettol-ing everything that comes into the house. Dettol owe him more of a thank you than me.
"Supermarket shopping is a military operation. It's like the hazmat gear you wear if you're defusing bombs! It's just a case of keeping us and other people safe."
Meanwhile, there's been a surge in sales of his first book, This Is Going to Hurt, published in 2017, which has been one of the top 10 Amazon bestsellers during lockdown as well as hovering around the top of the Sunday Times Bestsellers list.
We have to look for positives in what has been a gloomy situation, he offers.
"I think there's been good community cohesion, WhatsApp groups, people buying shopping for their elderly neighbours, the outpouring of love for the NHS, which will hopefully buy the NHS more time and look after the staff."
He hopes that learning from the crisis will help us deal with future pandemics.
"I suspect this won't be the last pandemic of our lifetime," he predicts. "Mistakes have been made and lessons will be learned.
"If there's a vaccine, then that changes everything, but until then I think this virus is with us for the long haul."
Kay is signed up for two more books and has completed his first children's factual book, Kay's Anatomy, a humorous look at the human body aimed at eight to 12-year-olds, which comes out in the autumn.
In the meantime, he is doing what he can to help. All profits from Dear NHS will go to NHS Charities Together to fund vital research and projects, and The Lullaby Trust which supports parents bereaved of babies and young children.
He's not sure he'll be hitting Captain Tom's NHS fundraising figures, though, he admits.
"Captain Tom set the bar pretty high - that's not where I've set my ambition," he chuckles. "But on a practical level I'd like to see it raise a lot of money for these charities."
Dear NHS: 100 Stories to Say Thank You edited by Adam Kay is published by Trapeze, price £16.99