SIMON Helberg, his wife, and their two-month-old son have come to Edinburgh from LA for the weekend. Unfortunately, their luggage has not done the same. This evening is the Edinburgh International Film Festival premiere of Helberg’s directorial debut, We’ll Never Have Paris, prompting him to have wardrobe worries on his spouse’s behalf.

“Hopefully her bag is going to arrive and she will not go to the premiere nude.” He pauses and grins. “But that would be quite outstanding.”

For a minute, Helberg has cast off the mantle of hip new director and is back in the mode of early Howard Wolowitz, his wannabe ladeez man character from The Big Bang Theory, the sitcom that has done for geeks and science what Friends did for sofas in cafes and Jennifer Aniston’s career.

But then people have a tendency to attribute roles to Helberg, the son of a casting director and an actor. We’ll Never Have Paris, soon to be released in the UK, has seen him compared to Woody Allen, and with his Stan Laurel physique and propensity to provide hot and cold running analysis of his thoughts and feelings as he has them, the Allen hat is not too bad a fit. He has joked that We’ll Never Have Paris is “neurotica” as opposed to 50 Shades erotica.

Yet it would be premature to pin the 34-year-old down too soon. With his first film in the bag, plus a two-year deal with Warner Bros Television to develop programmes, and a role in the forthcoming Meryl Streep movie, Florence Foster Jenkins, there is clearly more to Helberg than Howard. Like life on Mars, we just don’t know yet what it is.

The deal with Warner Bros TV, which also makes The Big Bang Theory, known to fans as TBBT, brings Helberg and his wife Jocelyn Towne together again as a creative duo. Towne made her directorial debut two years ago with the drama I Am I, in which Helberg acted. We’ll Never Have Paris finds the pair directing together from a screenplay by Helberg. The personal link to the project goes further than choosing which shots to take, however. Played out in the film is how Helberg messed up monumentally with Towne during their dating days, then went all out to win her back.

“It seemed poetic and maybe slightly perverse to tell the story of our break-up as a married couple now,” says Helberg over a late breakfast in an Edinburgh hotel. “There was something cathartic about that, and also something very balanced. The story is a liberal adaptation of what happened. I wish I could blame more on fiction but I did end up doing quite a few of those things – breaking up, she ran to Paris, I came grovelling back to her and she had met a violin-playing Frenchman.”

The couple had been together for four years when Helberg had what he describes as a “quarter-life crisis”. Was there another life out there that he was meant to be living? When telling the story to friends later, it was clear to him that he was not alone in suffering from green grass comparison syndrome.

“I realised that while it was a universal experience it also seemed that maybe I had the most catastrophic, self-destructive, disastrous version of this story to tell that I had heard. So I thought, well this has gone from tragedy to comedy and I need to tell this story.”

And he does, often in watch-through-the-fingers detail, with Melanie Lynskey playing Towne. Did he draw the line anywhere?

“I tried to be as vulnerable and as dangerously honest as I could. I guess the emotional journey, and the over-intellectualising, and the self-destruction and self-sabotage and self-indulgence, and all the words that have self in front of them, were all things that I had experienced and don’t particularly sound or come off that attractively at first glance. But in terms of drawing the line it was more about fleshing it out to make a better movie. There wasn’t really anything that we took off the table because it felt too personal.”

The low-budget film was made at a helter-skelter pace, with the couple working on it while having the new baby boy and looking after their toddler daughter. The children are now ages one and three.

“It’s just the nature of making this kind of movie. It ended up going incredibly well, although when we had our New York wrap party Jocelyn fainted from exhaustion.” The next day they flew to Paris and shot all night.

“There was nothing luxurious about any of this. It was unbelievably challenging at every turn. I think it’s the case for many movies but it really almost killed us. I lost 15lbs which is almost as much as I weigh. It was probably the hardest thing I think either of us has ever done. Not as much fun as it was an achievement, like climbing Everest.”

It must have taken some of the pressure off to know that there was the day job on TBBT to go back to. And what a day job. Since it began in 2007, the sitcom with four male pals (plus gal pals) as passionate about Star Trek as they are about physics, has rocketed up ratings tables around the world. The eighth series in the US (the ninth has just started airing there) brought in an average 19 million viewers per episode, making it the second most watched show in America after NBC Sunday Night Football. Here, one can tune into E4 almost any time night or day and catch an episode.

With large ratings come mega salaries. The three main characters, Sheldon, Leonard and his on-off girlfriend Penny, played by Johnny Galecki, Jim Parsons and Kaley Cuoco, are understood to be on $1 million an episode. After extensive negotiations last summer, The Hollywood Reporter put the salaries of Helberg and co-star Kunal Nayyar (Raj) at $800,000 an episode.

It’s a “once in a millennium opportunity” to be part of a show that is so widely watched and respected, says Helberg of playing aerospace engineer Howard. “Just the longevity of it, the quality, all things that make it not feel like a job at all. That’s incredible. At the same time it also paints you as a certain character that is kind of ubiquitous. You can’t go anywhere without it playing. So for all the positives of that there is also a little bit of an effort to be seen outside of that light. It’s like these golden handcuffs I guess, it’s a high-class problem if it even is a problem.”

He is still trying to wrap his head around the fact that millions of people across the world know his face courtesy of TBBT. Especially since the filming of the show remains just as it was when it started – shot on a small set at Warner Bros, in front of an audience of a couple of hundred people, with the same crew. “Then you come to Edinburgh and it’s like, it’s shocking. I can’t imagine anyone fully gets used to it or can grasp it.”

He certainly drew the crowds in Edinburgh, and impressed at the festival closing party by playing the piano. As you will see from We’ll Never Have Paris, Helberg is a pretty fine jazz pianist. He was delighted to have the film’s UK premiere there, and even more so when a picture of himself and Towne appeared on the front page of the Sunday Herald’s sister paper. “On the cover of The Herald in Scotland for We’ll Never Have Paris,” he Tweeted to his 842,000 followers. “Under a headline about haggis! #dreamsdocometrue. (The haggis story was a Holyrood-Westminster trade row thing, in case you won’t sleep tonight for wondering.)

Helberg was born in Los Angeles in December 1980. After a childhood on the west coast he went to the Tisch School of the Arts at NYU. Years of learning his craft followed, with stints in a comedy duo, Derek & Simon, in television and feature films, including Van Wilder: Party Liaison (2002). His first significant movie was Good Night, And Good Luck (2005), in which he played a television network page, and his first notable run on television was in the short-lived but critically acclaimed Studio 60 on the Sunset Strip. A comedy drama about a television show, the creator was Aaron Sorkin of The West Wing fame. Helberg was working on Studio 60 when he heard about a new show to be called The Big Bang Theory. He had to make a choice, and fortunately picked the right card: Studio 60 was cancelled.

To this day he is not sure why Studio 60 did not catch light. Timing might have been a factor, or the tone of the piece. “It was described as this gritty, behind-the-scenes look at a late-night sketch comedy show and it ended up becoming a little more politically based. I think people were a bit confused as to how to relate, what it was that they were watching. It’s just the way things go.”

He started on TBBT in 2007, the same year he and Towne married. Two years later he got the chance to work with the Coen brothers, in A Serious Man, playing a rabbi. Though a known face by now, he had to go through a long casting process. But worth it? He beams. “They are probably my all-time heroes and have been since I was a kid.”

Though he only worked a day he drank in the experience like a man who has just crawled through the desert and found a fridge full of beer. What struck him was the speed at which they worked. “They’re essentially two heads one brain.”

So he is more a Coens man than an Allen. That didn’t stop comparisons with Allen when the first reviews for We’ll Never Have Paris came out. Gary Goldstein of the Los Angeles Times called Helberg’s character, Quinn, a “vivid creation”. But reviewing for Screen International, Allan Hunter described Quinn as “a neurotic, blustering, hypochondriacal emotionally stunted florist who seems to have strayed from an early and infinitely superior Woody Allen film”.

Does he mind the Allen comparisons? “I have seen a couple of things that seem a little more maybe like digs or oh, it’s a poor impression of this or that. It doesn’t take a rocket scientist to see that I was influenced by him. Just look at me, first of all. Who wasn’t influenced by him that looks like me? It’s a very simple comparison at its core, the easiest thing to pluck out of the air. That being said, I’ll take it. He’s amazing. We didn’t try to emulate him or really anybody, it didn’t go any deeper than he’s a genius filmmaker and there are movies that we definitely were influenced by.”

After heading back to the US he was due to start filming the new series of TBBT. After that, a rest was planned. “It just kind of all happened at once. We finished Jocelyn’s movie, we had our first baby, we shot this movie, we had our second baby, and both movies came out at the same time. We’re a bit tired but it’s an amazing moment and we keep reminding ourselves how fortunate we are to have this much happening.”

Not that he rested for too long if the development deal with Warner Bros and his casting in Florence Foster Jenkins, in which he plays a pianist to the famously tone deaf singer, are any guide. Besides the piano, Helberg does a terrific line in impressions, chief among them Nicolas Cage. “He hasn’t come after me yet,” laughs Helberg when I ask if Cage minds. “I should probably start to keep my mouth shut.”

There goes that Howard grin again. “It only comes from a place of love.”

We’ll Never Have Paris opens in cinemas soon