"I think it's just very honest," he says of the film. "It's very truthful and I think not too sentimental, but at the same time it is about that kind of sentiment, so it is a difficult line to walk. But I think that if you're a miserable person, you won't enjoy it. But if you're capable of being happy, if there's happiness in you, it will hit at the right sort of degree."
Pegg's Hector is a London psychiatrist plagued by a very cinematic kind of ennui. Despite having a successful practice and a loving girlfriend, Clara, played by Gone Girl star Rosamund Pike), he just can't seem to find his inner joy. So he sets out to find it on a solo journey that takes him to China, Africa and the United States.
Pegg rejects the criticism that Hector is self-indulgent, or has no reason to be unhappy.
"As a character, he had to have somewhere to go. He couldn't just start out likeable and end up likeable. Boring. He has to have a journey, he has to have an arc. I think also to imply that if you're with Rosamund Pike you'd be happy is beside the point. You can be the richest guy and have the best-looking partner in the world and still be very unhappy."
Pegg is old mates with Pike, who appeared in his The World's End.
She's a good friend and someone I just like hanging around with. And that definitely informed our relationship in the film, because we were able to draw on our own friendship and that helped to communicate the degree of comfort that Hector and Clara had with each other."
Coming across as it does at times like a male version of Eat Pray Love, Hector and the Search for Happiness stands apart from Pegg's more comedically-focused work. Does the actor feel the way he is perceived by the film industry is evolving?
"I hope so. People tend to pigeonhole you in this industry. If someone's casting a serious drama, I probably don't come to mind, because I'm from a comedy world. I would love to go a greater variety of roles. I often see myself described as a comedian and I'm not. I haven't been a comedian for 20-odd years and I'm more sort of an actor now. And acting is acting whether it's comedy or drama. I would love to be able to do some more straight stuff. It's whether or not the audience thinks that.
With transatlantic success in America, Pegg is in a good position to assess the film's international prospects.
"We all thought, in a way, that the British audiences would be the least inclined to go with it just because it is very emotional and, as a nation, we like to hold it in and not talk about it. As a film we always thought it would do better among cultures that a more okay with emotions. It's a very global story, it literally goes from one side of the Earth to the other."
What: Hector and the Search for Happiness
When: At cinemas from today
- TimeOut