“The joy of Manchester weather,” he laughed. “I’m in Los Angeles so I’m going to be smug and superficial.

“It occasionally drops to about 60 degrees here and everybody freaks out.”

When he discovered that my football team is champions-elect Manchester City, he announced with a smile: “Man U is my team... we are at cross purposes already.”

But Gregg did score some brownie points after telling me that one of his favourite books from last year was Manchester-set Sirens by Joseph Knox.

The reason for our chat was not the weather, nor Manchester, nor our favourite authors. It was to celebrate the release of Hellbent (Penguin, £12.99) — the third book in Gregg’s thrilling Orphan X series.

For the uninitiated, Orphan X — AKA Evan Smoak — was taken from a foster home at the age of 12 and trained to be an assassin.

The first book sees Evan reinvented as the Nowhere Man, helping people with problems. He doesn’t charge for his service, but makes them promise they will pass on his phone number to someone else in need.

But the Orphans are being hunted and killed by someone who knows how they think and their weaknesses.

Gregg followed this with The Nowhere Man, which saw vodka-loving Evan kidnapped and being auctioned to the highest bidder.

Short story Buy a Bullet goes back to Evan’s first outing as the Nowhere Man.

Hellbent, to be published on Thursday, is about Evan wanting revenge when Jack Johns, the man who raised and trained him, is killed. Jack was the closest thing Evan had to a father.

And this time Evan has company, a teenage girl named Joey, who Jack died trying to protect.

“I spent a lot of time thinking what would differentiate Evan,” Gregg said. “I thought we never get to see Jason Bourne, Jack Reacher or James Bond in the real world.

“So I wanted to take an archetypal bad-ass character, but he lives in the real world with you and me. He lives in an apartment complex with neighbours, with all the annoyances and trivial matters which he is interacting with.

“We never get to see Bourne have an awkward confrontation with a single mom he has a crush on and we never see James Bond go home.

“I’ve taken a character hellbent on the protection of people who can’t protect themselves, but put him in the real world with us.”

He added: “He knows he can never have a normal life. He’s on the outside with his face pressed against the glass looking in at all these people having the kind of life he’d love to have, but can’t.

“When Jack took him out of the foster home at the age of 12 to make him an assassin, he told him, ‘The hard part is not making you a killer. The hard part is keeping you human’.

“The whole series is about the balance of that. What if you are the world’s greatest assassin, yet your moral compass is never broken?”

Gregg grew up in San Francisco with a dad from Boston and a mother from New York.

“I was not allowed to watch television growing up, unless the Boston Red Sox (baseball team) were on,” he said. “So I grew up reading and in libraries.

“My great-grandparents were immigrants from the Pale (in Russia); like a lot of others, they were running around trying to find somewhere safe to live.

“I come from a long line of Jewish, kind-of atheist, socialists. One of my great-grandparents worked with Samuel Gompers of the American Federation of Labor — so my background had a lot of very progressive and culturally Jewish aspects, but it wasn’t overtly religious because the emphasis was more on intellectual and cultural Jewish traditions and on helping the working people.

“I grew up with the food, the culture and the humour.”

He added: “But my grandparents weren’t bar or batmitzvah, although they identified heavily with being Jewish. Later in life, on one side, they became quite involved in their synagogue.

“And an aunt on my dad’s side married someone Israeli, so that side was more in keeping with religious traditions as well as cultural ones.”

Gregg knew he wanted to be a writer from a young age.

“I have mysteries that I wrote and illustrated in crayon going back to fourth grade (age nine-10),” he said. “It’s the only thing I ever wanted to do.

“I started my first novel, The Tower, as an undergraduate at Trinity College, Oxford, when I was 19.

“I got crazy lucky. I had an entertainment lawyer as I’d done an unpaid internship with him the previous summer — and it bought me one read. He sent it to M Night Shyamalan’s lawyer and he called me. They flew me to New York and introduced me to an agent. I had a preliminary offer for the book.

“Someone was flirting with it, but said I’d have to change my last name as it sounded too semitic.

“I said I wouldn’t do that and then Simon and Schuster came in and pre-empted it.

“I had my first book published, everything was super easy... then I wrote my second book, Minutes to Burn. It took me two-and-half years full-time to finish and I saw, in hindsight, how incredibly lucky I’d been with The Tower.”

His career choice was “a little puzzling” for his parents as, he said: “I come from a family of doctors and lawyers. They had in mind more that I would be an English professor.

“As I progressed and showed myself to be hugely committed to it, they came on board. They have been hugely supportive for a long time.

“My dad grew up in Boston medicine and my mom’s from a family of attorneys. I was this weird alien kid who wanted to write stories.”

Orphan X isn’t Gregg’s first book series. In 2004, he wrote the four-book Tim Rackley series.

He was halfway through writing the first book, The Kill Clause, when Harper Collins gave him a two-book deal — the first time he had sold a part-written book.

“I could see, once I got a head of steam up, how he could be a series character,” Gregg said. “But I always had an end in mind, so after four books I closed the loop. It didn’t feel as open as Orphan X.”

Gregg is pretty meticulous with his research. A lot of conspiracy theorists probably think he has inside knowledge due to the depth of his detail.

“I have friends who are Navy SEALs, Delta Force and Rangers,” he told me. “I do a ton of hands-on research, so Orphan X is based on how a lot of the programmes and operations have been funded and how they’ve been hidden.

“I’ve been on every gun that Evan has been on. I have a friend who is just like Tommy Stojack (Evan’s supplier of weaponry) in Vegas. He gets me on rocket-propelled grenades and combat shotguns.

“I’ve done mixed martial arts fighting... I’ve introduced my face continuously to the training mat. I hope this all helps to give the reader a front row seat to the action.”

He joked: “My internet search history would certainly raise some eyebrows, if I wasn’t a fairly well-established crime writer, as there is a lot of sketchy stuff there.

“If the NSA (National Security Agency) is listening to this phone call, I promise it’s all been for fictional purposes.”

Gregg has good news for Evan Smoak fans: “Orphan X will go as long as I want to write it.

“It has really connected with readers. I’m under contract for two more, but I’ll be writing more than that.

“I’ve already written a lot. Hellbent is my 19th novel. I work a lot in TV and films. I did comics, I wrote Batman. I wrote a young adult book series. If I feel like writing something, I’ll write it.

“But there is something incredibly gratifying about this series. I love it. There’s a reason it took me 15 novels to discover Orphan X. It’s the pinnacle of all the different sides of my career.

“A lot of cool stuff has happened over the last few years. Some weeks, I get two or three books to write blurbs for and part of my book tour is sponsored by a vodka company I mention in Hellbent.

“It’s caught fire in a way that is incredibly gratifying. It’s great when you think that something from your little skull is being reflected back from the world. It’s really exciting.”

He then whetted the appetite even more with this statement: “The next one will be the biggest thriller I’ve ever written.”

Fans are also getting frustrated by the non-appearance of the Orphan X film.

A year before the original book was published, Gregg sent it to actor Bradley Cooper and it has been waiting in development ever since.

“Bradley went on to write, star and direct A Star is Born with Lady Gaga, so his schedule went a little bit sideways.

“I’m working on Black Flags with him about the rise of ISIS.”

Gregg doesn’t believe Bradley will play Evan when Orphan X finally goes into production.

“I’ve been fairly protective of who is going to play Evan,” he said. “I don’t see him as a particular actor. He looks like the English hardcover picture from Orphan X. They captured how he is in my brain.

“He’s a lot like me, but obviously way more bad-ass. I’m average height, average build, average everything.

“I thought it would be interesting that instead of having him as a huge character like Reacher or incredibly handsome like Bond, I’d make him very ordinary looking and ordinary sized. He just blends in and no one really notices him.

“Evan is the best conceivable version of everything I could hope to be. There’s a lot in him that is relateable, but he does everything better than I do.”

He added: “When you work in TV, the writer is very important, but when writing a feature film, after you sell it, you are serving at the pleasure of the director and the star.”

Last year, Gregg wrote the hit film The Book of Henry.

“It took me 18 years to get it made,” he revealed. “I got director Colin Trevorrow, who had just come off making $2bn with Jurassic World and had really connected with the script.

“The minute he was on board, we got sized up and within three months we were shooting. You wait 18 years and then you get a big lever like that.”

Gregg, who is married with two daughters and “two giant Rhodesian ridgebacks”, says “I became a writer because of how much I love reading. I love Megan Abbott, Dennis Lehane, Robert Crais, Lee Child. It’s an endless list.

“I have 400 books in my to-read stack. I’ve resigned myself that, like my Netflix queue, it will never be empty.”

Although, judging from his admiration for Joseph Knox and love of Manchester, jumping to the top of his to-read list next month will be Knox’s second novel, The Smiling Man.

And no matter how much he tried to convince me, I still disagree with him about the casting of Tom Cruise as Jack Reacher in the films of Lee Child’s books.

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