Two years ago, very few people had heard of Matt Smith. Now he's an international star whose face is known to millions around the globe. And it's all because of one programme - Doctor Who.

No wonder he doesn't want to stop playing the Time Lord just yet.

"Why would I quit?" asks Smith after finishing his second season's filming. "I've got Steven Moffat writing scripts, but not only that - Toby Whithouse, Richard Curtis... all these great writers.

"And then of course, the part. I just love playing the Doctor. I've grown terribly fond of him. It's something I really enjoy."

He adds: "It's so funny, I read other scripts and I just go, 'Not as good as Doctor Who!'

"For me, it's a privilege to play this man. These parts don't come along that often. There was never any hesitation on my part to stay for another year."

That means Smith will be the incumbent Doctor when the show celebrates its 50th anniversary in 2013.

Lead writer Moffat has already hinted he has something big in store, but Smith won't be drawn on what that might be.

"Well, you saw the celebrations for Coronation Street... it was huge wasn't it? And Doctor Who is an institution, so to be part of the celebrations will be a real honour."

After taking its first ever mid-season break, the programme returns with an episode entitled Let's Kill Hitler, but fans shouldn't get too excited about the thought of a showdown with the Fuhrer - he makes only a brief appearance at the beginning and ends up being locked in a cupboard.

Instead, the main focus of the story is River Song. The last time we saw her, it was revealed she was the grown-up daughter of Amy Pond, the Doctor's assistant.

When the Tardis's inhabitants meet her again, she's an earlier version of the woman they've got to know over the years and believes her prime motive in life is to kill the Doctor.

"It's a very good episode," grins Smith. "One of my favourites, I think. There's a lot of pay-off."

Critics of the show will no doubt raise their eyebrows at the storyline, as the show has come under fire for becoming too complicated for children to follow.

"Ah, the critics," says Smith. "My response is it's like The Simpsons, which can be received on many levels. It's only as complicated as you choose to make it. One of the reasons it's doing well in America is there's great detail and many layers, and in a sci-fi culture that's what they want.

"My mum always asks me loads of questions about it, but she still enjoys it. Still, that's what's great about Doctor Who, everybody's got an opinion."

One thing most fans agreed on though is their admiration for Smith as the Time Lord. But the quirky actor almost didn't make it on to our screens.

A prospective professional footballer while growing up in Northampton, it was only an injury that prevented him from pursuing a sporting career.

On the advice of one of his teachers, he then took up acting and initially received acclaim for his for stage work, before going on to win roles in TV dramas, including Party Animals and The Ruby In The Smoke.

More recently he took on the challenging role of writer Christopher Isherwood in BBC Four's Christopher And His Kind, but it's playing the Doctor that has cemented his position as one of Britain's most in-demand actors.

"Fans seem very positive, but what they say to my face and behind my back, well, who knows?" he says wryly of his popularity.

So, what can viewers expect from the rest of this season? Well, according to Smith, they will be treated to a spooky hotel, a minotaur, David Walliams as a submissive mole-like creature, and the return of James Corden as the Doctor's former flatmate Craig Owens.

But Smith claims the grand finale is the one to look out for: "Episode 13 is, to my mind, pretty brilliant and mad." And sadly, that's all he's allowed to say.

Instead, he concludes by discussing the summer break. "I quite like it because I'm excited about Doctor Who coming back and it means we have another six weeks of Who, whereas we'd normally be finished now.

"It's quite an intriguing idea. Let's see how it works - we might do it again next year!"

EXTRA TIME - MATT SMITH :: Smith is a gifted footballer who had spells with Northampton Town, Nottingham Forest and Leicester City before a back injury curtailed his career. He supports Blackburn Rovers.

:: He appeared in the critically acclaimed play Swimming With Sharks in 2007, co-starring with Christian Slater and his Doctor Who colleague Arthur Darvill, who plays Rory.

:: Smith rubbed shoulders with Doctor Who alumni Billie Piper when he appeared alongside her on TV in Ruby In The Smoke, The Shadow In The North and Secret Diary Of A Call Girl.

:: His first major TV role was in the BBC series Party Animals, which focused on parliamentary researchers. He recently scotched the idea of bringing it back.

:: Smith's next TV project is BBC drama Bert and Dickie, about two mismatched rowers who won gold at the 1948 Olympics.

:: The second half of Doctor Who: Series Six begins on BBC One on Saturday, August 27