How do you go from being on the dole to directing London 2012's Olympic opening ceremony? Paulette Randall giggles. "The phone rings and a voice says, 'Hi. It's Danny [Boyle].' And I'm thinking, 'What does he want?'. Then he said: 'I might need a bit of help'."

And so Randall, whose very first, prize-winning play Fishing was directed by Boyle at the Royal Court in 1982, became associate director ("casting, rewriting scripts, everything Danny needed me on") of perhaps the largest live spectacle Britain has ever witnessed, watched by a reported billion viewers worldwide. "It was," she admits, fag burning, wine glass close to hand, "the best adrenaline rush of my life."

Randall, 52, meets me just as her production of Fences opens in the West End. August Wilson's Pulitzer and Tony award-winning epic stars Lenny Henry in a lead originated by James Earl Jones and performed most recently by Denzel Washington. Focused on the life and crimes of coulda-been-a-contender Troy Maxson, a washed-up former baseball player turned garbage man, the production "cements Henry's status as a serious actor", according to the Independent; "he is an actor of massive presence and emotional power," agreed this paper's Michael Billington. "Lenny's always been a star," Randall says, full of giddy pride at the reviews.

But this tells only part of the story of what makes this particular production special. Randall is the first black woman to direct a play in the West End. "It's my biggest achievement," she says, "'course it is, but you never know what's around the corner, do you? I'm nowhere near done." Randall has had plenty of successes: she produced Desmond's and The Real McCoy on television in the late 80s and early 90s, is a former artistic director of Talawa (the country's longest surviving black theatre company), and has directed smash-hit musicals, Shakespeare and new writing in London and beyond for more than 20 years. She also managed to wangle herself a deal with the late August Wilson to have exclusive rights to direct his work in the UK; she's currently on the sixth of his 10-play cycle. But she's still nervous about seeming too pleased with herself.

"I do have a track record now," she reflects. "But I am still so disappointed that there aren't more of me out there." Black actors on screen and stage have come a long way since Randall graduated in community arts at the Rose Bruford college in 1981. But she is visibly anxious about what all this means – "fluke, more like it," she remarked in a 2004 public debate about theatre's "new black renaissance". Her co-panellists, Kwame Kwei Armah and Stephen Luckie were aghast.

The question has arisen once again during the last few months, with black theatremakers again making headlines: just as Fences transferred to the West End, the National opened its own production of James Baldwin's The Amen Corner; a new adaptation of Alice Walker's The Color Purple has just begun previews at the Menier Chocolate Factory.

But Randall argues that this is hardly the norm – behind the scenes, things in theatre are as tough for people from minority-ethnic backgrounds as they ever were. "I'm thrilled about [it being easier for actors], but there's no room for growth and development of designers, sound engineers, directors." What about the multiple courses offered in colleges these days? "What's that got to do with art?" she retorts. "There were 17 or 18 [multi-ethnic] theatre companies working in London when I started, where you could move around and learn – there's only three now."

Randall's own history in the industry is far from straightforward. In 1990, she abruptly quit after the opening night of the musical Five Guys Named Moe, feeling – she said – undermined by Theatre Royal Stratford East (she later revived her production in 2010 with Clarke Peters, to considerable success). In 2004 she resigned from Talawa after bitter fall-outs with the board over where the company's future would lie.

She makes no apologies for being outspoken. "I think, culturally, sometimes people don't get it. Certainly, my background is quite vocal and quite loud, and that's not anything to be afraid of. If you don't understand it, I can see maybe you would find it intimidating, but it's not."

And when I ask actors and former colleagues, Randall is considered infectious company. You can hear her before you see her, a great clanking jangle of her jewellery (heavy, silver, never comes off) followed by a huge, red-lipsticked laugh. She doesn't so much work a room as operate a gravitational force field around her.

For Randall, born to Jamaican parents in south London, being "gobby and a showoff" has always come naturally. "It was working in Brixton market, that was my real first understanding of theatre, just the characters you met and stories you heard." She was 11 when she started helping out in a bric-a-brac shop on Saturdays, and kept coming back throughout drama school. "It was a great place to work, my parents were right to let me do it. I loved it."

Randall still lives in south London, a couple of miles from where she grew up, in the same flat she's lived in for the last 30 years. She gestures at the theatre, puffing away, joyous about the show. It must feel good to be here, I say. She laughs. "The best thing? People have to listen to you. You don't have to shout."