Peter Capaldi is recovering from a Doctor Who injury. I initially assume when we meet at the Charlotte Street Hotel that his unlaced black Loake boots are a punkish subversion of the ones he wears on-screen but actually he’s seeking relief after key-hole surgery to his knee.

“The injury comes from running down corridors and swivelling round quickly,” he says with a lemon-sucking grimace. “When I first met Matt Smith he was on crutches from exactly the same problem.”

However, if ligament damage is the price he pays for being the 12th regeneration of the Doctor, he seems happy with it. Happy too with embracing the sort of advanced geekery that goes along with Doctor Who — such as paying a surprise visit to selfie-demanding Whovians queuing over night at Comic Con like some latter-day Henry V visiting his troops on the eve of battle.

No doubt there’ll be similar levels of fandemonium at the ExCel centre later this month when he takes to the stage at the three-day Doctor Who Festival. Such are the burdens of carrying the BBC’s crown jewels, a franchise that has been licensed to 189 countries (and wildly popular in the US) and is the most successful show in the BBC Worldwide portfolio.

Occasionally, of course, a fan will bring up his most famous pre-Tardis role as The Thick of It’s Malcolm Tucker. But as agonising as it may be for those (like me) who fell in love with him as master of the baroque expletive (“I’d love to stop and chat to you but I’d rather have Type 2 diabetes”) 57-year-old Capaldi is enjoying his role as the avuncular extraterrestrial too much to contemplate doing much else. Including dealing with the life admin that has accumulated since he took on full-time Timelording in 2013.

“I’m Doctor Who! I shouldn’t have to stand around in this queue,” he declares, with a teasing scowl. “Or wait in for a pair of shoes to be delivered. Or sort out the recycling, which I had to do yesterday. My family keep my feet on the ground but I don’t want my feet on the ground!”

"A lot of the people I play are excluded from the mainstream and I think that’s because of the way I look."

By family, he’s referring to his wife, Elaine Collins, an actress turned BBC TV producer, and their daughter Cecily, who recently graduated from university and is training in London to be a teacher. (He recently had to move them from his beloved Crouch End to Muswell Hill because his old house was so near a school that he was constantly spotted by junior Whovians.)

I ask him where he would go if he could time-travel back to any part of his life. “When you’re middle-aged, like I am, the past becomes more colourful,” he says, and yet despite the technicolour craziness of his current existence he eventually alights on the moment in 1983 when he first met Collins working for Paines Plough Theatre Company: “I just loved meeting my wife. We were both in a show together so that was terribly exciting. I’d like to re-live that.”

It’s a sentimental confession from an actor who almost never plays a romantic role, usually portraying men burdened by power (King Charles I in the Devil’s Whore) or witty mavericks (such as Tucker or Randall Brown in stylish BBC series, The Hour.) In some quarters (ahem) he’s considered thinking woman’s totty — so why doesn’t he play more husbands or lovers?

“You’re looking at it,” he says, circling his gaunt features. “I like characters who are strange and on the edge. A lot of the people I play are excluded from the mainstream and I think that’s because of the way I look. But who wants to watch an everyman all the time? I’m not that bothered if I never do another scene in a kitchen.”

He recently won praise from female fans for insisting that it would be “creepy” to add any sexual element to his on-screen relationship with his much-younger sidekick, Clara, played by Jenna Coleman.

Doctor Who: who could be the new companion? 8 show all Doctor Who: who could be the new companion? 1/8 Sophie McShera As Jenna Coleman leaves Doctor Who to star in an ITV period drama, wouldn’t it poetic for a Downton star to jump ship for the BBC sci-fi series? Sophie McShera’s journey as Daisy, becoming increasingly assertive from her timid origins as a kitchen assistant, makes her stand out as a contender. Matt Writtle 2/8 Gemma Chan The star of Channel 4’s Humans is no stranger to high concept sci-fi. Chan delivered a stunning turn as sentient robot Anita / Mia, and has the perfect mix of strength and warmth to join the Doctor on his travels. John Phillips/Getty Images for Jameson 3/8 Kaya Scodelario The former Skins star, currently starring in the adaptations of the Maze Runner YA novels on the big screen, would be a real change of pace for the Doctor’s assistant. Scodelario is tougher and less whimsical than recent companions. She's also starring in the new Pirates of the Caribbean film though, so something tells us she might be a little bit busy. Imeh Akpanudosen/Getty Images 4/8 Maisie Williams The announcement that Maisie Williams would be appearing in the new series of Doctor Who was exciting enough, but the thought of her permanently joining Peter Capaldi in the TARDIS gives us tingles. BBC 5/8 Holliday Grainger After impressing in The Borgias and starring recently as the titular character in the BBC’s recent adaptation of Lady Chatterley’s Lover, a prominent role in Doctor Who would help Holliday Grainger cement her rising star status – as well as breaking her out of her period drama type-casting. AFP/Getty Images 6/8 Thomas Brodie-Sangster A new female companion often means a male companion too – a Rory Williams or a Danny Pink – and Maze Runner and Game of Thrones star Thomas Brodie Sangster would be a great fit. In fact, Who fans will remember his emotional turn in Series 3 two-parter Human Nature / The Family of Blood – and the fact that former bit-part players are often cast as companions means that he’s a strong contender for a comeback. John Phillips/Getty Images for Jameso 7/8 Jessica Brown Findlay Downton Abbey’s Lady Sybil broke everyone’s hearts when – spoiler alert – she suddenly died in the third series. Jessica Brown Findlay’s rebellious but warm performance is exactly the sort of dynamic that the best Doctor Who companions manage to strike. Tim P. Whitby/Getty Imagea 8/8 Scarlett Moffatt OK, we know this one’s never going to happen. But can you imagine Peter Capaldi’s Doctor flying through space and time, and getting teased by Gogglebox’s hilarious Geordie Scarlett? Don’t pretend you wouldn’t tune in for that. Channel 4 1/8 Sophie McShera As Jenna Coleman leaves Doctor Who to star in an ITV period drama, wouldn’t it poetic for a Downton star to jump ship for the BBC sci-fi series? Sophie McShera’s journey as Daisy, becoming increasingly assertive from her timid origins as a kitchen assistant, makes her stand out as a contender. Matt Writtle 2/8 Gemma Chan The star of Channel 4’s Humans is no stranger to high concept sci-fi. Chan delivered a stunning turn as sentient robot Anita / Mia, and has the perfect mix of strength and warmth to join the Doctor on his travels. John Phillips/Getty Images for Jameson 3/8 Kaya Scodelario The former Skins star, currently starring in the adaptations of the Maze Runner YA novels on the big screen, would be a real change of pace for the Doctor’s assistant. Scodelario is tougher and less whimsical than recent companions. She's also starring in the new Pirates of the Caribbean film though, so something tells us she might be a little bit busy. Imeh Akpanudosen/Getty Images 4/8 Maisie Williams The announcement that Maisie Williams would be appearing in the new series of Doctor Who was exciting enough, but the thought of her permanently joining Peter Capaldi in the TARDIS gives us tingles. BBC 5/8 Holliday Grainger After impressing in The Borgias and starring recently as the titular character in the BBC’s recent adaptation of Lady Chatterley’s Lover, a prominent role in Doctor Who would help Holliday Grainger cement her rising star status – as well as breaking her out of her period drama type-casting. AFP/Getty Images 6/8 Thomas Brodie-Sangster A new female companion often means a male companion too – a Rory Williams or a Danny Pink – and Maze Runner and Game of Thrones star Thomas Brodie Sangster would be a great fit. In fact, Who fans will remember his emotional turn in Series 3 two-parter Human Nature / The Family of Blood – and the fact that former bit-part players are often cast as companions means that he’s a strong contender for a comeback. John Phillips/Getty Images for Jameso 7/8 Jessica Brown Findlay Downton Abbey’s Lady Sybil broke everyone’s hearts when – spoiler alert – she suddenly died in the third series. Jessica Brown Findlay’s rebellious but warm performance is exactly the sort of dynamic that the best Doctor Who companions manage to strike. Tim P. Whitby/Getty Imagea 8/8 Scarlett Moffatt OK, we know this one’s never going to happen. But can you imagine Peter Capaldi’s Doctor flying through space and time, and getting teased by Gogglebox’s hilarious Geordie Scarlett? Don’t pretend you wouldn’t tune in for that. Channel 4

“It’s ridiculous that we get these old guys with young women draped round them. When I started Doctor Who and we were doing photoshoots we’d be asked if Jenna could just lie down there while I, you know” — he leaps up and acts out a young woman sprawled coquettishly about while he gets to stand and look powerful over her. “I had to say, ‘Look, that’s just not what we’re about. The relationship between my Doctor and his companion is one of deep love. But it’s a strange sort of platonic bond. It becomes clearer and more moving as this particular series goes on.”

Capaldi saves his most Tucker-esque sneer when discussing sexism in the industry. “Of course it’s sexist. Most of my peers have partners their age, so if we have a dinner party with a bunch of actors, the wives or partners are largely the same age. Then you see your friends on screen and they are suddenly with some extraordinary young lady who wouldn’t be at the dinner party. It’s ridiculous.

“It is true that women reach a certain age when people decide that they’re not useful anymore as actors. There are a few significant theatrical roles that they might be viable for. That’s not fair, it’s not right, it’s not a proper reflection of what goes on in life.”

He says he’s not averse to a male sidekick once Coleman bows out in December — and he doesn’t rule out a female doctor with a male sidekick in the future — but “it depends on who plays them”. Capaldi isn’t keen on speculating on his possible replacement because as far as he’s concerned, there’s no vacancy.

He rules out any return for The Thick of It — even if he agrees that the current state of politics is ripe for satire. “I don’t know where my character would fit into it. Politics is so much about the now that I’m not sure there’s an avenue for Malcolm to reappear. And I wouldn’t want to revisit him unless he was central to the endeavour.”

Surely a series set among Jeremy Corbyn’s opposition would be fun? He remarks that the Labour leader himself would be “an amazing character to play”. Is he a Corbynite, then? He refuses to reveal his politics but as someone drawn to outsiders he’s found Corbyn’s emergence “absolutely thrilling”.

"Even on your break, everything is Doctor Who-related. Artistically, I hunger for something that is different."

“I love the way the political orthodoxy is being challenged. It seems to be becoming — rightfully so — the spirit of the times. It feels vital and compelling. There’s a range of professional politicians and opinion makers who say certain things in politics can’t happen. And then these things happen because people want them to. That’s a wonderful thing.”

He admits craving roles beyond Doctor Who. “Even on your break, everything is Doctor Who-related. Artistically, I hunger for something that is different.”

He reminisces about the bohemian London that still existed when he first arrived in the early Eighties, when Soho was a “swamp” and he would spend his days hanging around there smoking Gauloises and hoping to meet John Hurt or acting with Daniel Day-Lewis in Dracula. The pair would be taken in and fed by the mothers of the working-class girls who sold tickets for their play at the box office.

“I loved being in touch with all of that part of London life. You get distanced from that as you become successful. I’ve never felt drawn to Mayfair.”

He has a particular yearning to play an artist. “I’m interested in Francis Bacon and how he came to be. And Lucian Freud was very interesting.”

He fancies being involved in a TV show that subverts the crime genre: “I love that idea of taking a standard police show and giving it a philosophical or supernatural timbre.” Although he would consider a Shakespeare stage role, he fears coming across as the “dunce at the back of the class” as he’s never had any classical training. “I have given up trying to make things happen. If people want me in the movies, that’d be lovely.”

After the Sony hack revealed discussions over a Doctor Who feature film, it’s entirely possible — but there are no firm plans as yet. He wants to squeeze as much pleasure out of the role before the franchise sheds its scales (as it always does) and looks towards a 13th Time Lord.

Capaldi recalls that a few nights earlier, on Halloween, young trick-or-treaters who came to his house were spooked when Doctor Who greeted them. “In a few years’ time, once I’ve left the show, I’ll miss it so much I’ll be coming to the door in my costume.”

Follow Johanna Thomas-Corr on Twitter: @JohannaTC

The Doctor Who Festival is on November 13-15, doctorwhofestival.com