"I'm so sorry, it seems like I'm the only one here capable of reading a map," he says, sounding somewhat like the character Douglas Petersen, from his Man Booker prize-listed book Us.

While I, and millions of readers worldwide, loved his best-selling novel One Day, I didn't like Us.

It told the story of Douglas and his wife Connie, who embark on a meticulously planned yet ill-fated tour of Europe with their 17-year-old son Albie before he leaves home for university.

Connie's just announced she's on the verge of leaving Douglas, but she'll go along with the trip if they get divorced when they return home.

Us was a little grim, the story perhaps a little close to home, when it was released in 2014. While One Day had the darkest of twists, it was still a novel full of optimism and hope.

While One Day made us cry out of sheer emotion, Us made us cry because perhaps we realised our own middle-aged was as grey as the Petersen's.

"Us was kind of ... not downbeat but ... not cynical either," says Nicholls, the family on their way.

"But maybe a too realistic portrayal of the downsides of long relationships, of marriage, of families."

His own father died while he was writing Us, his children were little, parenting became a focus, in his own life, and in the book somewhat.

"I thought, when it came to the next book, I didn't want to deal with this subject matter again or write about love in this tone.

"I wanted to write something more joyous and wide-eyed, optimistic i suppose."

And the book is Sweet Sorrow, set in the 16th summer of Charlie Lewis who, having finished school, is almost literally knocked over by his first love.

"First love seemed like a good subject because, by definition, it only happens once," Nicholls says.

"There's this unique quality and flavour that is divorced from the realities of everyday living.

"It's the first time you've had these feelings so it's a new sensation, a new set of emotions, and that was much more appealing than writing about divorce and separation and midlife crises."

"I wanted to write something more joyous and wide-eyed, optimistic i suppose."

Sweet Sorrow is a glorious book. Set in the summer of 1997, there's the typical historical references to music, popular culture, world events, such as the death of Princess Diana (was it really that long ago, was that the end of innocence?)

Charlie, not really knowing what he wants to do with his life, is out riding his bike when he almost runs over Fran Fisher. He is smitten. Fran is filling her summer with Shakespeare, part of an amateur theatre troupe, The Full Fathom Five, who will be performing, of all things, Romeo and Juliet, at summer's end. Would he like to join in?

He would like to get to know Fran Fisher, so with nothing much else happening, he tags along.

Sweet Sorrow will have you yearning for your own first love. Can you remember who it was? That first stirring of new emotions, the butterflies, the hormones.

Nicholls can.

"I didn't necessarily particularly draw on my own experiences," he says, although elsewhere he has said Sweet Sorrow is his most personal book.

"My 16th summer was nothing like Charlie's, it was quite dull and grey. I spent it working in a factory making coffee machines and went on a three-day cycling trip with my friends Baz and Neil. There was no real-life Fran."

His first love was over by the summer of 1983, when he was 16, "but I do remember the yearning and intensity of it all.

"I also remember the extreme power of friendship at that age, that feeling of boredom, of waiting for something to happen, desperately wanting some adventure to begin, I felt all of that."

He grew up in Eastleigh, Hampshire, the middle child of a maintenance engineer and a council worker. He, unlike Charlie, was a self-admitted "swot", prone to quoting Monty Python. In his first year of university at Bristol where he studied drama and English, he spent a summer staging Shakespeare's A Midsummer Night's Dream.

He did work as an actor, studying in New York, but once wrote "I'd committed myself to a profession for which I lacked not just talent and charisma, but the most basic of skills. Moving, standing still - things like that."

He then turned his hand to script writing making his name with the hit comedy drama Cold Feet. Just this year he won a BAFTA for his television screenplay of Patrick Melrose, starring Benedict Cumberbatch.

He says the screenwriting trains him to write better stories, plot and pacing, and his trademark chronological jumps in time. He wrote the screenplay for the 2011 movie adaptation of One Day, starring Anne Hathaway and Jim Sturgess, he's currently working on scripts for the television dramatisation of Us.

He's not sure if he enjoys seeing the books on the screen.

"I'm very pleased when it happens, don't get me wrong, but the process is really tough and painful. No matter how faithfully you adapt something, you're always going to lose material and that's hard when you've slaved away on a book for many, many years."

Does he ever worry that he'll be remembered as the man who wrote love stories? (Would that even be a bad thing?)

"I have written about love a lot, but it's not always the main story of the book," he says.

"I talk about parents and children, husbands and wives, mothers and fathers, mental health, and friendships.

"I can't imagine a book where love plays no part because it is something that informs so many of our experiences, it's a vital part of our lives.

"I did try writing a novel that had no relationships at all and I found it very hard and a bit grey and grim, I don't think I'll do that again."