Noel Clarke walks into Edinburgh's Caledonian Hotel wearing a smile and an Iron Man T-shirt.

Half an hour later I'm not sure either is totally appropriate.

He should be happy. Later this evening he has a film - a science- fiction actioner called The Anomaly - premiering at the Edinburgh Film Festival before going on a general release. He's the lead, the director and one of the producers. On his arm there are eight tattooed notches, one for each film he's been involved in over the last few years, ranging from Kidulthood and to Fast Girls. And though he doesn't mention it he's got an appearance on an ITV drama on the horizon.

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And yet within a minute of turning on the tape he mentions a review of The Anomaly he's just seen that writes it off as "over-ambitious" and it clearly rankles. He returns to that word again and again in our conversation, deconstructs it, tries to see what it means, what he thinks is behind it. Although he says otherwise ("it's water off a duck's back"), he doesn't come across as made of iron. He seems bruised.

The movie is a tricksy time- travel movie with action hero leanings. Ask him why he wanted to make it and he says: "I just really liked the fact that it was ambitious but still contained. And I fell in love with it. I loved that you could do something so epic. There are massive moments when you're in one country and then you're in another and my feeling was 'just go on a ride with it'."

For all its flaws - and I'm afraid there are a few - you can't deny it has a sense of scale. I'm a little astonished when he tells me that the budget was even less than he had to play with on the lo-fi sci-fi thriller Storage 24 he wrote and starred in. "A lot of people are saying 'oh, it's a low-rent version of Inception, a low-rent Matrix'. They're comparing it to massive American movies and it's a low-rent British film so actually thank you very much. The point was to do something that looked more [expensive] than it actually was."

Why, I want to know, did he take on so much, though? Acting - including fight sequences done in one take, which he admits "is very physically demanding. It's almost full contact and if you mess up near the end you have to start again" - directing and producing all on a limited budget. "This goes back to much bigger conversations. I kind of feel sometimes there isn't a choice. All I ever wanted to be was an actor. Writing happened because I wasn't getting the roles that I wanted and then directing happened because directors weren't directing my scripts the way I thought they should be. And producing happened because I realised people were getting paid a lot more than I was for doing a lot less work.

"And also I've worked with a few charlatans who gave me a really bad experience. To this day - and I can tell you this now because I'm fine about it - to this day I've still not been paid for"

He probably couldn't have afforded Idris Elba or Chiwetel Ejiofor, he says. "Also, the fact is if I don't play this role a black guy would never get this role. It would go to Sam Claflin or someone like that. Nothing against him. I think he's awesome."

The Anomaly was Clarke's chance to play a black action hero, then. "And it's never mentioned once [in the movie]," he says proudly. Is cinema becoming any more colour blind than it was? "No, we're 100 per cent not. I don't necessarily agree with a lot of actors who say 'oh you have to go to America'. They can say that now because they've got their TV show over there. A lot of them kept quiet for 15 years. 'Mate, you weren't saying that when you were here'. I'm here and I'm saying you don't have to. Ashley Walters said you don't have to. But you have to work hard. I don't claim to be the best at anything but I know I work hard."

Where did that drive come from? "It's just something I have, I dunno. I think from my mum. She had to raise a boy in the Kidulthood area. I've got two boys now. It's not easy. When you have children there's a moment of clarity where you suddenly go, 'I now respect my mother so much'."

Brought up in Ladbroke Grove, Clarke was a teenage gym instructor who first appeared on our screens when he was 22 in the Channel 4 comedy drama Metrosexuality. He became a familiar face when he was cast as Billie Piper's boyfriend, Mickey, in Russell T Davies's revival of Dr Who, and then found success with the Kidulthood films inspired by his own love of Pulp Fiction, Amores Perros and Doug Liman's film Go and the world he saw around him. "Growing up here I didn't see anything that really represented me. Then I started seeing Boyz n the Hood and they were American but you're like 'I get it. My mum talks to me like that'."

He's 38 now. What does the word ambition mean to him today? "For me ambition is always striving to achieve better, consistently working, consistently trying to improve what you do.

"Not everything's going to work but at no point has any of us tried to waste money. Everything we do we believe in. It baffles me when people go 'it's over-ambitious'. I want to teach my kids to reach for the stars all the time. One of them is six and he's great at maths. Be an accountant, boy. Be the best accountant you can be. I don't want his boss to go 'you know what? I don't like you. You're a bit over-ambitious. What job tells you don't try too hard? But of course, in film if you try to reach for the stars you're 'over-ambitious'. It baffles me. You know what it's like? It's like telling Solomon Northup not to play the fiddle. 'Get back in the field and pick the cotton. How dare you learn to play the fiddle? Know your station, man.' That's essentially what it's like."

None of this is said in anger. It's more exasperation. A sense that he's not appreciated. He says he doesn't take it personally. "I've got children now. I've got better things to do."

What would that 16-year-old gym instructor think of the man he has become, I wonder? "He'd recognise the drive and ambition and he'd feel exactly the same way if someone told him you're being over-ambitious.

"He'd say, 'don't be ridiculous. There's no such thing."

The Anomaly goes on general release tomorrow.