Ken Loach's 2016 social realist drama, I, Daniel Blake, was one of the year's most talked-about films. A critical smash and multiple award-winner (including the prestigious Palme d'Or at Cannes) for its damning portrayal of Britain's welfare sanctions regime, it was such an important film for Loach to make that he came out of retirement specially to do so. We hear from two of the film's actors who just so happen to be veteran comedians returning to this year's Fringe: Dave Johns, who plays the titular role, and Chris McGlade who narrowly missed out on the lead and took on a smaller part.

Listening to Dave Johns speak so exuberantly about his experience in the title role of Ken Loach's I, Daniel Blake, is infectious. 'I'm 61 and I won best newcomer at the Empire film awards!' he marvels. 'I beat Tom Holland – the new Spider-Man – who's 22! The awards have been just crazy. You've got people like Nicole Kidman coming up to you and going, "I watched I, Daniel Blake with my mother and your performance was incredible." And you just stand there going, "will somebody punch me in the face? I think I'm going mad".'

A newcomer to film he may be but Johns has performed at the Fringe a number of times since his last regular stand-up show in 1999, with notable appearances in Guy Masterson's lavish theatrical productions, 12 Angry Men, One Flew Over the Cuckoo's Nest and The Odd Couple. Masterson's once-regular Fringe highlights, taking a classic Hollywood film and reworking it for the stage with a cast of comedians (and once Christian Slater), have sadly since fallen by the wayside.

'Owen O'Neill always loved 12 Angry Men,' explains Johns. 'He got in touch with Guy and that's how I got on board: they were only casting comedians. And it was Guy who got me the audition with Ken Loach. So the seeds for I, Daniel Blake were planted in 2003.' Inspired by those lavish productions, Johns turned his hand to writing, penning an adaptation of The Shawshank Redemption with fellow writer / comedian / actor O'Neill.

For someone who has been working so hard for such a long time, earning plaudits as a comedian, actor and playwright, Johns seems genuinely astonished that it's all come together, particularly at his age. Before I, Daniel Blake came along he'd even been considering winding things down.

'The comedy circuit in England at the moment is not as vibrant as it used to be. A lot of the clubs have closed. Good comics will always work but it's not as regular as it used to be. I took my daughter to Scarborough and there were donkeys on the beach. I started talking to a bloke and I thought about running donkeys on the beach, working the summer. I've done 30 years of stand-up!'

But then the Loach film came out of the blue and gave Johns a whole new lease of life. 'Not only has the film changed people's perception of the subject matter of austerity, poverty and food banks, but it's also changed my life. It's taken me to a place that I never expected to be. One moment I was doing a gig in Hull for £140, travelling all day on the train, staying in the Travelodge and doing a stand-up show to stags and hens. Then the next minute I'm at the Cannes Film Festival and in a lift with Woody Allen! I used to go to my room and just look in the mirror and go, "you're in a coma and you're in the hospital and this is all in your head".'

With more film roles under his belt and in the pipeline, Johns is still marvelling at the differences between stand-up and film. 'Stand-up's very immediate,' he explains. 'You know exactly if you're doing well in stand-up; you know if your jokes are working and if not then you can adjust them. With film, once you do it you've got to take the director when they say, "OK, let's move on". And then once you see it back in the cinema, you can't change it: it's there forever. I think that's why a lot of directors don't watch their movies, because they'll always see something that they don't like, and they can't change it. Now, if I do my show up in Edinburgh and something doesn't work, I can change it the next night.'

Thinking again about his first full stand-up show at the Edinburgh Fringe this millennium, Johns has a back-up plan if it all goes wrong. 'I think I've got a nice show and I'm going to have fun with it. But if it all goes tits-up I'll go back to the donkeys: I've still got the licence application!'

Comedian Chris McGlade has long been driven by a fierce determination to combat social injustice. In 2004 he took a break from comedy to lead a long and fractious campaign, opposing the construction of a large housing scheme earmarked for Redcar's Coatham Enclosure. 'We fought this corrupted scheme, we won in the House of Lords and changed the law regarding open spaces,' he explains. 'We uncovered corruption and scattered them to the winds.'

McGlade was unable to celebrate victory for long before an appalling personal tragedy shattered his life. 'My dad was murdered in 2011', McGlade explains matter-of-factly before setting out the extraordinary mix of fortune that befell him. 'I fought the political campaign from 2004 to 2010 and then I started to tentatively gig.' One day McGlade happened to meet a theatrical agent on a train. 'I said to him I've always wanted to be in Billy Elliot and he said, strangely enough, "I'm just going to meet the casting director for that and I think you'd be perfect for the role of George, the boxing coach." And I got the part. Halfway through the run, my dad was murdered at his home in Redcar and it knocked me for six. But within a week or so I was back in the show because it was the biggest break of my career. Dad had a strong working-class work ethic and that rubbed off on me so I finished the contract.'

Naturally enough, events finally caught up with McGlade. 'The magnitude of it all just hit me like a brick wall,' he explains. 'I didn't even come out of my bedroom for about four months. In about September I got some counselling from the homicide victim support people which did me the world of good. I realised I wanted to go back on stage and make people laugh. But I'd been offstage for so long, so I started gigging around the country for nothing to get a feel for it. Every time I went on stage it was like looking up a mountain. Then in 2014 I got a call: they said Ken Loach wants to see you for the lead role in I, Daniel Blake.'

Sadly for McGlade, he narrowly missed out on the lead role to Dave Johns. He was gutted. 'They said, "you don't look like a 59-year-old heart attack victim!" Because, since dad's murder I train all the time for fitness and for focus: I never want to go back to the time when I was lacking motivation.' He admits to feeling envious when he first saw Johns step onto the set in costume, but he quickly refocused. 'You only get what you're supposed to have; that's the philosophy I've adopted, and I was calm after that. I thought [about Johns]: good on ya, cos he's north-eastern lad as well. And to work with people like Ken and Paul Laverty was just like a dream come true.'

McGlade remembers his inauspicious Fringe debut in 2008. 'I was in a venue that was past Haymarket station in an old church. It was a fab venue but I was in this little office and I think the most people I had in was four. I did it to no people one time. Then in 2010 I did the Fringe at the other end of town at a football social club.'

This year he's finally made it to the heart of the capital. 'I talk about all the things going on in the world and the things I see going on in our country, but I always try to put a Teesside perspective on things,' he explains. 'I called my show Infant Hercules because it appertains to the area where I'm from. William Gladstone came up to Middlesbrough in 1862 and said that the area was the 'infant Hercules': like an industrial giant ready to wake up. I suppose it was going to be like the latter-day 'Northern Powerhouse'. When they closed our blast furnace in Redcar in 2015 I thought, well that's a bit of a contradiction: they call us the Northern Powerhouse yet they've gone and closed this glass furnace that had been open about 180 years. It had been around when Gladstone was there. I'm proud of this area and I think we get done down. We're always a poorer relation to the Geordies and the Mackems. It's got lots of tragedy and lots of humour. I love the place.'

Dave Johns: I, Fillum Star, Pleasance Dome, 5–27 Aug (not 15, 22), 7pm, £12.50–£13.50 (£11.50–£12.50). Previews 3 & 4 Aug, £9.50
Chris McGlade: Infant Hercules, Just the Tonic at The Caves, 3–27 Aug (not 14, 21), 11pm, £5 (£4) or Pay What You Want.
6 x 6 x 6, Pleasance Dome, 2–28 Aug, £9–£10 (£8–£9). Previews 2–4 Aug, £6.