LET'S begin with a discussion of power politics and a Great British Bake Off-flavoured analogy. You join us as Paulette Randall is discussing the skill set required of a theatre director. As someone who has directed shows in London's West End she knows what she is talking about in this area. So Paulette, what I want to know is, I tell her, do you have to be a dictator to be a director. Is absolutist rule necessary on stage?

"You're always a dictator but you have to pretend you're a dictator in a democracy," she laughs. "You sometimes feel quite manipulative but you hope you're being manipulative to a good end. You have to encourage people's ownership of what they're doing.

"Someone has to make a decision on whether it should be pink, green, yellow or blue, whether the door should open on the left or right; all those boring things. But it's about working with all the other creatives as well and then how you marry that with all the actors you have carefully selected."

"It's about trying to make a fantastic cake in a way," she adds, getting all Mary Berry on me, "because every time you start with the same list of ingredients – doesn't matter if it's a musical or a thriller. Ultimately you go 'well, if I get all these things in place this cake should rise.'"

Paulette Randall is, I have decided after half an hour in her company, a proper tonic. Later in the day she might even buy you a gin to go with it if you're lucky. But it's morning, earlyish and we're drinking coffee in a café opposite London's Shaftesbury Theatre. Neither of us have gone for the cake option.

Today Randall – a born-and-bred Londoner who calls herself Pete by the way – is all silver bangles, full-on fashion-forward eyewear and a gulping rush of conversation, whether it's discussing directing episodes of Holby City ("Great, except I don't really like blood. I know it's fake but oh my God …"), why you should all go and see Five Guys Named Moe when it opens in the Spiegeltent in Edinburgh (she's directed it, you see), the idea of musical theatre as a gateway drug or the heartbreak of Brexit.

When we speak she is halfway through rehearsals for Five Guys Named Moe, which is one of the main events of Edinburgh's Christmas celebration this year. "We're doing it in a tent. That in itself will be different. We're really embracing the idea and playing it pretty much 360 degrees, which is a nice challenge to have."

For those not in the know, Five Guys Named Moe is a West End and Broadway musical with a book by actor Clarke (The Wire) Peters, which features the music of Louis Jordan, one of the greats of America's swing era. It's the latest revival of a 1990 show from a time, as Randall points out, before we even used the phrase "jukebox musical".

Randall has history with the play. Not all of it good. She is 55 now. Way back when, she was down to direct the original show. But it didn't work out. She left just before it opened in bad blood.

What actually happened? "I was in my 20s and I'd never done a musical before and of course, in the pursuit of excellence, wanted to get the best people. I got a fantastic choreographer who then got an amazing vocal arranger.

"Bear in mind," she cautions, "this is my perspective. But they just felt I wasn't the right person to be directing. Which is ridiculous. But they had an idea and having worked on a lot of musicals themselves they kind of felt there was a way of doing it and I clearly was young, female, didn't know what I was talking about. They just felt I was a bit of an obstacle."

"I did go and see it a year after. I'm not bitter. And I thought they would have changed everything that they didn't like but they hadn't at all. It was still the show that I had done."

Did the experience knock her youthful confidence? "Yes of course it did. I'm human. I knew that somewhere deep down I was going to do it again. I kept saying at some point I have to do another musical because I have to put that experience in a better place.

"And then six years ago I got the chance to do it again so it was just lovely. And now I'm still working with Clarke and we're still coming up with some new little changes which keeps it fresh."

Is there a sense of revenge in all this, Paulette? "Absolutely not. Who cares about revenge? You're not going to get anything lovely out of that."

Well indeed. Will you get anything lovely out of Five Guys Named Moe though? Here's my problem, I tell her. Musical theatre. Not a fan. It's a bastard form, isn't it? Neither one thing nor another. What is it good for? How do you defend it?

"I don't think it needs defending," Randall suggests quite simply. "Not everything is for everyone."

That said she argues, if you do like musical theatre, "this one's a cracker. It's a laugh".

I suppose one defence for those of us averse to the form might be that musical theatre is a kind of gateway drug for the real thing.

"You could argue that's what panto does," she points out. "Which is like this in a way. People I've met saw this show when they were seven or eight with their parents and had a great time. And what's not to love about something you can take the family to and have a great time, safe in the knowledge you won't have to try and cover their ears or their eyes and hopefully they'll get something out of it."

Growing up in South London to Jamaican parents, Randall, it's fair to say, would have been an unlikely theatrical advocate. She insists she only applied to drama school when she was 18 to win a £5 bet. "I was working in Brixton market at the time and £5 was a lot of money. I thought 'I can apply for this. I don't have to do it.'"

"I'd done O Level drama. Didn't do very well. I liked playing, but never wanted to do anything serious with it because I never knew what I wanted to do."

One all-day audition changed all that. She'd found something she wanted to commit her future to. More or less. "The first year was a bit of a struggle because I found a lot of the stuff we had to do – like exploring your space in a bubble – a bit wanky."

But she knew this was the world she wanted to work in. She just needed something more solid, more grounded than exploring bubbles. Perhaps that was inevitable given that she was growing up black in a country that was riven by racism in the late 1970s.

"I'd been part of the Anti-Nazi League. The offshoot of that was Schoolkids Against Nazis. I'd managed to make it to head girl. I'd go to demonstrations and organise stuff. All of that was really important to me. So when I went to drama school I couldn't just do foolishness. It had to be rooted in something, something that was of value or worth, without being too precious about it."

When she graduated she set up Theatre of Black Women along with Bernadine Evaristo, who would later make her name as a novelist, and Patricia Hilaire. The fact that they considered it necessary says something about the inclusivity or otherwise of British theatre in the 1980s. "We were preparing ourselves. You either be proactive or you shut up. We were proactive."

Would black drama students emerging from drama school today find it a different world? "I think we would be crazy to say we haven't seen a change. There is much more of a variety of faces, whether it's in adverts or dramas. But I think there is still room for improvement. And as for behind the scenes, that's quite shameful really. Still."

Is it simply a problem of middle-aged, middle-class white men calling the shots and commissioning material that reflects their own concerns? "That still goes on and you can understand that but it should be challenged and it should be consistently challenged. You shouldn't wait for some very nice white man to think, 'Oh, actually …'"

What have people struggled with most, her gender or the colour of her skin? "That's a really hard one because neither of these things can I change nor would I want to. I'm complete. I can't really separate it. I suppose if I had an African-sounding name people would immediately go, 'Oh well, she's black. But I don't know. I couldn't split me.

"Sometimes I don't want to be seen as a black director. I just want to be seen as a director. Equally, I don't want to be seen as a female director. But there are pluses because occasionally you get a script where being female or being black gives you a bit of a leg-up."

Her path to directing proved slightly circuitous. Why did she not stick to acting? "Oh God, I've never stuck to anything."

Instead she started writing, winning a prize that meant an extract of her play was performed at the Royal Court. She sat in on rehearsals. Some guy called Danny Boyle was directing. That's when she realised she wanted to do what Boyle was doing. "And then I discovered I was better at it than any of the other things."

She has tried her hand at "other things". She produced the Channel 4 black sitcom Desmond's and BBC2's black and Asian sketch show The Real McCoy. She was also one of the associate directors of the Olympics Opening Ceremony. Actually, she was on the dole when Danny Boyle phoned to ask her if she would take part.

"There are still gaps," she admits. Is that good or bad? Does she enjoy the downtime? "How can unemployment be fun? What's the matter with you?" she asks. "It would be nice to think I can plan my life ahead a little bit. If you're worried about these potential gaps go and find a full-time job quite frankly."

Three years ago Randall became the first black woman to direct a drama in the West End when she helmed August Wilson's play Fences, starring Lenny Henry. Has there been a second? "I don't think so. Which is frustrating. I don't get angry so much. I get passionate about wanting things to change only because I just think with more variety it makes the world a more interesting place."

Variety is politically problematic at the moment though, isn't it? You have to wonder did Brexit change her idea of Britishness? "Of course it does because this is not my home, this is not the way I see my home.

"But then you have to be careful. I'm a born-and-bred Londoner and London is unique but I get that it's part of a united nation and something went wrong if people feel so disenfranchised and rejected. And that was heart-breaking because I really thought we weren't looking at the world that way, looking at ourselves that way."

This is cheery, isn't it? There must be something to be hopeful about? Well yes. In her profession things are changing. She points to another black British director, Amma Asante, now getting to film big-budget films like Belle and A United Kingdom for example.

But more needs to be done. "I think there are still voices out there that aren't being heard. If I put my black hat on, what stories would I like to do? Well, something that's not necessarily historically based and something that doesn't have the police involved and doesn't have drugs and guns. It would be really nice to go, 'What about a love story?' Other elements that make us human beings. That would be nice.

"Otherwise why train actors if they're just going to have to pick up a gun and run? I could pick anyone off the street really."

What does Paulette Randall want? A bigger slice of that cake for everyone would be nice.

Five Guys Named Moe is on at the Festival Square Theatre until January 7. For more details visit edinburghschristmas.com