James McAvoy's sister, Joy, on big brother's influence

Now, it had been widely assumed the actress from Glasgow housing scheme Drumchapel had been handed the part, thanks to a little bit of nepotism. “People always assume that,” she says, with a wry smile.

However, that’s not how her personal script played out at all. “I didn’t even tell my brother I was auditioning for the part. I didn’t want him to put in a good word or anything. And I didn’t want him to feel bad if I didn’t get it. I wanted the role on merit. And I got it on merit.”

She adds, with a wicked grin; “I know the director loved the bit I added on at the end of the audition, which I can’t reveal because it was quite rude. But it was quite funny.”

McAvoy discovered later, that once she’d landed the role the director had a difficult phone call to make to the star of the movie. The part of Estelle called for the McAvoy siblings to play lovers in a sex frenzy. Abuse abounded.

“The director called him [James] and said ‘We’ve got this girl for the part but we need to run it past you because it could present acting difficulties.’ James said ‘What? Is she an ex-girlfriend or something?’ The director said ‘No, it’s your sister.’ But James was more than happy to go along with it.”

James McAvoy said later it was the most difficult scene he had ever acted in. “For me, it wasn’t so hard to do,” says the actress.

“I could forget he was my brother because he was so in character. And it made me step up my game. Even off camera, he was still Bruce (the druggie, bipolar cop.) He kept it going.”

The reflection offers the chance to segue into the dynamic between the McAvoys, the siblings who grew up with their grandparents after their parents split. Was it the usual brother-sister rivalry? Did they thump each other? “Oh, aye,” she says, grinning; “All brothers and sisters do that. You get the deidies a lot [dead arms from little flat punches] and the Chinese burns.” She grins; “Can I say that? Is it PC.?” She adds, laughing; “Anyway, he toughened me up. He got me ready for the real world.”

Her voice becomes a little more serious. “In recent years, I’ve been able to ask his advice a lot. And at times when I’ve been quiet I’ve been able to work as his PA on a couple of films and that’s like an acting masterclass for me. I get to sit by the monitors and watch what he does with a script.”

The notion of becoming a performer however arrived in her 10-year-old head independently of her brother’s love of acting. She recalls she would stare at the TV screen, watching her favourite movies such as in Grease or Dirty Dancing “over and over again” until she learned all the lines. “I would go to bed and recite whole movies as the lead characters.”

Her school, St Thomas Aquinas, had a “brilliant” music department, which encouraged the teenager’s singing, but keen to act the then 14 year-old took herself off to Scottish Youth Theatre.

“I loved it. And I knew I wanted to be an actress. But my poor granddad would be saying ‘Are you sure you don’t want to be a doctor or an architect, Joy?’ I said, ‘No. I want a life of perpetual struggle. I want to be an actress.’”

McAvoy however remembers the early impact big brother’s new life (he was around 16) had on her. “I’d never read a film script before and he was working on The Near Room with David Hayman at the time. I would sneak into his bedroom and try to learn the script, seeing his lines all highlighted, and then put it back when he came home. This script represented the Holy Grail for me.”

The Holy Grail world began to become a reality when McAvoy was accepted for drama college. But when she exited the doors of the college for the last time, McAvoy discovered the doors of film and television were hard to prise open. “I had trained in theatre at drama school and it was great; I learned how to find a character, how to get over stage fright, how to hold an audience – but there weren’t courses in TV acting at the time – and when my agent put me up for the film and TV roles I blew them all. I was delivering all my lines really big, and as a result I got nothing.”

She had to re-learn. And she did. “I got books and read up on Acting for Camera. You have to teach yourself.” She adds, grinning; “I want to say sorry to all those casting directors who had to sit and listen to me in that first year.”

McAvoy isn’t afraid to be self-deprecating. When asked if she’s ever followed the Hollywood route to landing roles – which involves dressing in character for the audition, wearing a bikini if the part calls for it – she offers a knowing grin.

“Wear a bikini – no. But I did mess up once when I went to audition for the Ken Loach film The Angels’ Share. After casting director Kahleen Crawford set up a meeting with him I scraped my hair back, wore no make-up because I figured a

Ken Loach film would be all dark and gritty. But it wasn’t right to pre-empt what they may have been looking for and I blew it.”

But sometimes you have to stand out? “Really, if that’s the case the next time I’ll go in wearing a Christmas jumper,” she says, laughing.

McAvoy laughs easily. But an understandably awkward silence arrives when I ask how her mother felt about her becoming an actress. Now, McAvoy has shown incredible courage in simply turning up for this interview because her mother passed away this month. (She had been ill for some time.) To give McAvoy immense credit, she attempts to answer. “She was just really happy for me . . ., “ she says, her voice breaking and tears forming in her eyes.

She composes herself and adds in crumbling voice: “What I can say is she was very supportive. She was amazing . . . ”

McAvoys voice cracks again. In pre-Weinstein days I would have given her a cuddle. Nowadays, I push on to easier territory. I recall the last time we met she was working in Oran Mor, the theatre-bar in Glasgow’s West End. “I loved working there,” she says. “I’d love to work more regularly as an actor but that’s the nature of the business. Most of the people I trained with are doing day jobs, then little acting gigs. But I’m lucky in that

since moving to London three years ago I’ve landed a lot of voice-over

work for the likes of video games

or bank’s tutorials so that’s my

day job. And I get to be American or English. But I’m not above working in a bar.”

Some very good acting work has come along however. McAvoy enjoyed a stint in BBC Scotland’s River City (“my granny really loved that”) and the likes of Channel Four’s cop drama, No Offence.

Right now, McAvoy is set to star in Two Doors Down, Gregor Sharp and Simon Carlyle’s hit comedy that’s as cutting as a hairdresser’s new scissors. McAvoy plays the newbie on the street, Michele, whose partner Alan is played by the irrepressible actor-wrestler, Grado.

The pair landed the role when they revealed great comedy chemistry together in auditon. “Love comes in all different guises,” she says, smiling of the unusual matching. “We did have a little chat and created a back story. We decided we were school sweethearts, and we’re still madly in love.”

Her own love life is also running perfectly. “I’ve met a lovely guy in London and the poor boy has never dated an actor before. He has found out that I do need a bit more attention than any of his previous girlfriends. ‘Have I had a call back? I’ve just got an audition! I need to learn my lines. Do them with me.”

She adds: “He runs a gym in Shoreditch and that’s a great motivator for me because he’s up and training at 6.30am, and he gets me up and into shape. The only minus is he is six foot three and eats loads.”

What’s gleamed from Joy McAvoy is she’s a grafter, a woman who works hard and is thankful for whatever joy life offers. At the moment, she still can’t believe she’s had the chance to work alongside “acting royalty” such as Elaine C. Smith.

“I don’t need to be famous,” she says, in soft voice. “So long as I can pay the bills and I don’t have to worry about eating. I’ve never had to be rich. I would just love to be a regular working actress. If I could have a tenth of my brother’s success that would be amazing.”

She says she owes Drumchapel. “It gave me a lot of great grounding.” She adds, with a smile: “It would have been nicer to have a little more to do there.”

McAvoy hasn’t called on big

brother for help, but she admits he has been an incredible example of possibility.

“I may not have stuck it out [acting] for as long as I did if he hadn’t done so well,” she admits.

“The idea of us not coming from much, growing up in Drumchapel, yet he made it, regardless . . . this really gave me hope that it can happen to people like us. He’s always been a great role model to me.”

Two Doors Down, BBC 1 Scotland, 9pm