It’s freezing in London, three-layer weather, but Russell Tovey is wearing only a T-shirt. So what, I say, steering the 33-year-old inside a warm-looking cafe, you don’t feel the cold these days? Now that you’re…

Now that the actor is broader, musclier, or to use a phrase that was popular in his native Essex when he was growing up, a unit. If you’ve kept a mental picture of Russell Tovey from his early-career days as one of the National’s original History Boys, or from his later screen stuff, in Him & Her and Sherlock – well, take that mental picture and stretch it. Photoshop-enlarge the neck. In Banished, a new BBC drama that starts this week, Tovey plays a gnarly, red-cheeked outdoorsman called James Freeman, one of the first British convicts to be deported to Australia. The type of role, Tovey reckons, “I never would have got before. When I was a skinny little rat.”

I go into this, Tovey’s new heft, because the bulking up turns out to be more than just a result of actorly ambition (casting directors in mind) or a thirtysomething’s resolution to take a gym membership. Bent over his coffee, angling his shorn head to show me the scar, Tovey tells a distressing story about when he was 18, and was attacked by strangers, and got stabbed in the head. “I’d been in a pub in Romford, getting the train to my to meet my parents in Brentwood. I was wearing a cardigan. At that time you never wore a cardigan in Romford.”

On the train, two men sat opposite and asked him the time. Then they showed him their knife. “One said to the other, ‘Are you going to cut him or am I?’” Tovey got thumped a few times; another passenger pulled the emergency cord; he was slashed above the ear before it was over. The actor tells all this without prompting, and with lots of close detail, as if it happened last week. “Pouring blood everywhere… I didn’t know where it was coming from, I thought they’d cut my throat… Another passenger was giving me sugar out of a sachet.”

His parents rushed to hospital straight from a fancy-dress party, and so came through A&E dressed as a cowboy and a Gypsy. Tovey tells this last part with a smile. But he says it took him about a decade, all told, to shake the effects of the attack.

“If they’d asked for my wallet or phone I would have understood it. But it wasn’t anything to do with that. They just wanted to fucking hurt me. And trying to get your head around that, later… For years afterwards I was left with an insecurity. I’d see groups of lads, even in a pub, and I’d feel intimidated. It’s a weird thing but if you talk to other people who’ve been through it, you give off a vibe. The pack can sense you’re weak. It made me so frustrated. And going down the gym, discovering the gym three years ago, and really going for it – I feel a lot more in charge. I needed to exorcise that feeling of being a little scared, skinny rat.”

If you’ve followed Tovey’s acting career (and he’s one of those exceptionals, I think, who encourage long-term, almost parental interest from role to role) you might have noticed a gear change a couple of years back. Tovey, who lives with his boyfriend in east London, started playing gay men. He appeared at the Royal Court in The Pass, about a footballer coming to terms with his homosexuality, a part he’s also just filmed for the screen. And he took a cameo in Pride, Matthew Warchus’s 2014 film about gay activists in 1980s Wales. Then there’s his ongoing role in Looking, a comedy-drama made with characteristic excellence by HBO.

Now about halfway through its second season on Sky Atlantic, Looking follows the muddled fortunes of five gay men in San Francisco. No grand coming-out stories here. No episodic Aids scares. The obvious intention in Looking is to show, delicately, amusingly, day-to-day life in a specific contemporary milieu. “I’m a massive fan,” says Tovey. “I watch it over and over again. I make my friends watch it. And I’m in it.”

He told his parents he was gay when he was 18. Then two years later Attitude magazine rather starkly told the rest of us, after Tovey gave a noncommittal answer to their interviewer. Still it took him 10 years to play gay on stage and screen – about the same amount of time it took him to get over being attacked in Essex. Were the two connected, I ask? “Yeah, 100%. I never before felt… ready, or knowing where I wanted my career to go. I never felt in charge of anything. And then it got to a point where I thought: now.”

Anyway, he says, “If you’re gonna go gay, do it on an HBO show. Do you know what I mean? Quality.”

Tovey’s career has been stimulated, for sure, by a good amount of quality writing. Britain’s Andrew Haigh wrote and directed many episodes of Looking, and Banished is a long-cherished project of Jimmy McGovern. Tovey was for five years one of the leads, with Sarah Solemani, in Stefan Golaszewski’s gleeful, cheeky BBC3 sitcom Him & Her. Before that he appeared in Russell T Davies-era Doctor Who, plus a corking Sherlock episode by Mark Gatiss, and he benefited from Alan Bennett at his best when The History Boys began its original run in 2004. Even the cheesy adverts that got Tovey his start in the business, as a pointy-eared kid with a penchant for supermarket goods, were prizeworthy. “My big advert was for ketchup. I come home from school, cook my brother and sister their dinner, ride my bike in the garden. Remember that one? People cried at that advert. It won awards. I was 12.”

I used to be insanely envious of Dominic Cooper. I always wanted to play his part in The History Boys Russell Tovey

Tovey came away from the ketchup gig with a Sega Megadrive, bought with his £900 fee, and a sense of acting being his vocation. He missed chunks of school at his Essex secondary to make a kids’ TV show, Mud, and as a result of the absence didn’t always have a lot of friends. “I was so envious of everyone who went to Sylvia Young Theatre School. I wanted to go but my dad flat-out refused. He thought I’d become some tapdancing freak without qualifications. And he was right in a way. I’m glad I didn’t go. That might have changed…”

Tovey thinks carefully about what he’s going to say next. If I had to guess, watching him fidget, I’d say he’s weighing up whether to be honest at the risk of causing offence, or whether to divert and say something bland. He chooses to risk offence. “I feel like I could have been really effeminate, if I hadn’t gone to the school I went to. Where I felt like I had to toughen up. If I’d have been able to relax, prance around, sing in the street, I might be a different person now. I thank my dad for that, for not allowing me to go down that path. Because it’s probably given me the unique quality that people think I have.”

The quality he means is a rare kind of pigeonhole-resistance. “I get told, a lot, that I’m kind of carving my own path. That there are not many actors who are out and are able to play straight, and gay, and everyone’s OK with it.”

He points to his role in the McGovern drama. His character in Banished is “totally heterosexual. There’s no part of James Freeman that fancies another man.” And its broadcast will correspond, roughly, with that of Looking, in which Tovey’s character, Kevin, is frequently seen, let’s say, horizontally. After one particular episode last year Tovey called his mum to ask if she’d been watching. “Yes,” she said, “I saw your little bum going up and down.” She only had one question: “Did they spray on that sweat, or was it real?”

Tovey’s dad has opted out of Looking. “He got to episode four and said: ‘I love you, you’re great… It’s not for me.’”

The actor has spoken in the past about the difficulties his parents had when he first came out: their automatic fear their son would contract HIV. Their suggestion, even, that he seek a cure. He tells me now: “I didn’t feel like they should get it straight away. Why should they? It took a long time for me to come to terms with it. But we’ve all been on a journey together and now it’s great.”

Recently he showed his mum around San Francisco and took her to Folsom Street Fair, an annual celebration of leather, fetish gear and other forms of BDSM culture. “She loved it,” says Tovey. “Imagine my mum, with her motherly handbag, looking down at these guys with piercings through their dicks. Taking photos. Facebook actually removed three of the pictures from her page.”

At the end of her visit, he says, they took a walk together along the Golden Gate bridge, where they were approached by a young man on a bike. “He said, ‘Because of you, and Looking, I know who I am.” His mum asked the boy if his family knew yet, and the boy said no. “So my mum gave him a cuddle and a kiss.” She knew there were large conversations to come.

It’s about time for us to leave the cafe and head back out into the cold. In a minute the actor will self-consciously put on a shiny jacket over his T-shirt, now that I’ve made a big deal of it. Before he goes he tells me one more story, another from his “skinny rat” days. Tovey was in New York, The History Boys playing on Broadway. Its young cast, including an on-the-rise Dominic Cooper as the handsome lead, were very close, says Tovey. Also very competitive. “And Cooper,” Tovey recalls with a smile, “was a fucking nightmare.”

“He was suddenly being courted. He’d have scripts for fantastic movies and amazing TV things, and he’d leave them in the wings for us to see.” Tovey helped him learn lines with an American accent, “being supportive, because he’s my mate, but also insanely envious”. One day Tovey got a call from an American agency himself. They wanted to meet! “So I went along, sat down. They asked, ‘How’s Dominic Cooper?’” Tovey thought it was introductory chit-chat. “Then they asked, ‘Is he happy with his representation? If you hear that he’s not happy, will you let us know? Cool, well it’s nice to meet you, take care.’ And they left. It crushed me.”

How long did it take, I ask, before you felt you were getting a bit of what Cooper was getting? American interest, all that. Oh, says Tovey, about 10 years. “Round about now. The HBO thing has certainly helped.” As has the gym.

“I always wanted to play Cooper’s part in The History Boys. Only nobody else saw me like that. The audience would have been, ‘Er, hang on a sec. Are we supposed to find that guy attractive?’”

Now, Tovey says, he tunes in to new episodes of Looking when they’re on. “And it’s the first time I can objectively watch myself and go: ‘Yeah, he’s hot.’”

Banished starts on BBC2 on Thursday, 9pm