The TV adaptation of One Day, starring Leo Woodall and Ambika Mod, shot straight to No 1 in the UK Netflix chart when it premiered earlier this month. Now, the book it was based on is back in the bestsellers chart, too – 15 years after it was first published. Author David Nicholls says he was influenced by romcoms including When Harry Met Sally when he wrote the story of Dexter and Emma, who meet every year on St Swithin’s Day over the course of 20 years. “I had a desire to write something full of emotion and affection, that owed a debt to romantic comedy, but was also about life and death, the highs and lows of our professional lives, the insecurities of your 20s.” “I thought I was writing the book for my generation, people who grew up in the 70s and 80s,” Nicholls, 57, says. “But when it came out in 2009 I knew it was being read by a lot of younger readers, including Ambika who read it as a teenager. Now my daughter comes in from school and tells me that her friends are watching and falling in love with Dexter and Emma, even though their story is receding further into the past, and that’s really thrilling for me too.” Even Kim Kardashian has recommended the show to her 364m fanbase on Instagram “if you want a good cry”. This is particularly amusing to Nicholls. “Isn’t that weird. A lot of it is about what it feels like to work in a lousy Camden restaurant in 1991 and living in crappy bedsits … I love the idea of her sitting and watching it on a massive television.” Nicholls paid tribute to the team behind the show, who he called a “pleasure” to work with. “It’s often quite an adversarial relationship between a novelist and the people adapting their work, because a big part of the job is discarding material. You can get very defensive about that and feel as if someone’s coming into your house and rearranging the furniture. But I never felt like I was losing control.” It had also felt risky to put a story like this on television, across 14 episodes, because “usually a show like that relies on twists, big events, murders, all kinds of plot developments”. But he was pleasantly surprised that viewers not only made it to the end, but watched it two and sometimes three times. After all, what’s more dramatic than love? “I’ve always thought that it’s often the biggest thing that happens to you, meeting someone and falling in love. It’s the thing that shapes your life,” he says. Though Nicholls has written a number of popular books, including 2003’s Starter For Ten and 2014’s Us, and worked on several films and TV shows such as 2018’s Patrick Melrose, One Day is by far his most popular work. The book has sold over 3m copies in the UK and 6m worldwide, in 40 languages. But the recent spike in interest has been somewhat of an existential experience for the writer. “I wrote the book when I was about Dexter’s age at the end of the novel, in my early 40s. It was in the spirit of nostalgia for my 20s and 30s,” he says. “I had just become a parent so I was saying goodbye to that part of your life which is all about starting your career and dating and having fun.” But when he looks at it now, he says he feels “much more rueful” about the passage of time. “The way it accelerates, the friends I’ve lost, the people no longer with us, the regrets I have. There’s a double layer of nostalgia associated with it now – nostalgia for the period of time it covers, from 1988 to 2007, but also nostalgia for the time in which I wrote it. “I’m almost another 20 years older and it’s much more about the things that escape me. For me now, One Day means something slightly different, something slightly more melancholy.”