Mark Millar leads a double life. In one, he is a husband and a father living in a prim Glasgow suburb; in the other, he is something of an international man of mystery. When the two worlds collide, it tends to cause ripples of frowning disbelief.

In his working life, Miller is a comic book writer, and an outrageously successful one at that. His storylines for the Fantastic Four, the X-Men and Spider-Man are so popular that he now works for Marvel, the US publisher, on his own terms. Four years ago, he set up Millarworld to publish three comic books of his own, with another two to follow. The movie version of one of them, Wanted, will be released later this month.

The £33m film stars Angelina Jolie, James McAvoy and Morgan Freeman. It centres on the story of a doleful office worker, played by McAvoy, who discovers that his late father was a super-assassin and becomes one himself.

Having visited the set in Prague, Millar can drop into conversation anecdotes about chatting with Jolie in her trailer and finding her watching Little Britain DVDs, or the time he shared with her the delights of Coatbridge, his hometown.

“You hear of actors being surrounded by their PAs all the time, but I didn’t find Angelina like that at all,” says Millar. “You just realise she’s a 32-year-old girl who’s really nice.

“She said to me, ‘What is this place Coatbridge you talk about’, and I said, ‘Aw it’s beautiful. Just imagine mists over the hills’, and I gave her this shortbread version of Scotland. I just saw McAvoy <NO>Glasgow] looking at me, grinning.”

Miller has learned, though, to keep anecdotes about his famous friends to himself. “I found myself saying, I was telling Angelina...’. I learnt very quickly not to mention it, even with friends, because I have at times seen them looking at me funny,” he says.

There is an unbridled sense of delight that pours from Millar, a kind of gauche feeling of good fortune. He talks of comic books and movie adaptations with the gushing thrill of a teenager, but there is also a hard edge of corporate grittiness.

Millar, 38, is working on another 10 creative projects, alongside the five he has already devised. He is involved in setting up franchises to distribute his work and computer game tie-ins. All this so that he can retire at the age of 45.

Early retirement is a common theme of his interviews, but the older Millar becomes, the more his retirement age keeps being pushed back. He once told a journalist that he would stop writing comics at 30.

His contract with Marvel ends this month. Although it has offered him another deal stretching to 2013, which his wife, Gill, is keen for him to sign, he only wants to commit to another 12 months.

The success of Wanted, which he says has sold about 1m English-language copies and is the highest-selling creator-owned comic book of the past decade, has become a lucrative diversion.

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