Image copyright Getty Images Image caption Motsi Mabuse has previously judged on Let's Dance - the German version of Strictly

The Strictly Come Dancing panel is an extremely delicate thing to balance.

At one end, there's Bruno Tonioli. Flamboyant, excitable and enthusiastic, he acts effectively as the contestant's friend and ally on the panel. At the other sits Craig Revel Horwood, the stern-faced, far more critical judge who gives highly technical feedback and relatively low scores.

The middle ground can, appropriately, be found in the middle. This is where the experienced head judges like Len Goodman and Shirley Ballas have been placed, mediating and adjudicating when the vote is split.

And it's here viewers will see Strictly's newest recruit, Motsi Mabuse. It was announced earlier this summer that she would be stepping into the shoes of Dame Darcey Bussell, who has left the show after seven series.

Mabuse is currently a judge on the German version of Strictly, a former South African and German Latin champion herself, and the sister of Strictly professional Oti Mabuse.

"I've danced before, so I know how it feels to stand in front of judges and be critiqued," Motsi tells BBC News ahead of her Strictly debut. "I know how it feels to work hard and to work with a celebrity. I've danced all my life, so I know what type of work is needed.

"And I know the power of words. That means I'm really quite aware of what's going on with the celebrity and I just want to keep them quite encouraged and to find their limit."

Image copyright PA Media Image caption L-R: Craig Revel Horwood, Motsi Mabuse, Shirley Ballas and Bruno Tonioli

Mabuse will sit alongside head judge Shirley Ballas,"being the wall between Craig and Bruno" as she puts it, adding with a smile: "I may have to kill Craig!"

The 38-year-old's appointment has been broadly welcomed, but viewers have little idea what kind of temperament she will have as a judge.

She isn't well known to British audiences in the same way that some of the other bookies' favourites for the job were - like Ashley Banjo or Anton Du Beke.

After she was announced, many fans headed to YouTube to get a flavour of Mabuse in action. But because all her previous TV judging has been in German, no footage existed of her speaking English as a judge - which has just made British viewers all the more curious.

"I know, that's great isn't it!" Mabuse laughs, clearly enjoying the mystery and intrigue that has surrounded her appointment. But, she adds, viewers have little to worry about.

"I'm not the kind of judge where you get away with everything, because I know my basics," she says. "But I'm the judge where, if you emotionally capture me, then you've got me, I'm in your team.

Image caption Motsi Mabuse will replace Dame Darcey Bussell (second left) on the judging panel

"I think restricting myself to saying, 'Okay, I'm from the dance world, I'm only going to talk about dancing' is not the point. Dancing is never about steps or straightening your leg or performing the spin correctly. Dancing is about the message that you give, the energy, the vibe, whether people spontaneously just get up [when you dance]."

Mabuse's appointment hasn't been without controversy, as her role on Strictly will require her to critique a member of her own family. Strictly pro Oti Mabuse has previously been paired with Graeme Swann, Jonnie Peacock and Danny Mac on the show, but now she and her new celebrity partner will be graded by her own sister.

"That's going to be the hardest thing for Motsi," Len Goodman told The Sun recently. "Can you imagine if Oti is in the final two in the dance-off?

"Whatever decision she makes, Motsi will get criticism. If she puts Oti through then people will say she's doing her sister a favour. If she votes her off they will say she didn't want to be seen to be keeping it in the family."

Motsi says: "I think, for me, it's about professionalism. I'm not judging Oti, because I know my sister is a brilliant dancer, like all the other dancers on the show. It's not about them. It's about the celebrity learning to dance.

"There is a word in German, called gerechterweise, which means fairness. I need to be fair, it's just the part of my personality. So if I feel like I'm [showing favouritism] to Oti, it's not fair for Oti, it's not fair for me, and it's not fair for the other celebrities.

Image caption Strictly pro Oti Mabuse, Motsi's sister, was partnered with cricketer Graeme Swann last year

"So if Oti should win or something, it's important that she has a feeling that she did it on her own and not because her big sister gave her a five point lead. She would feel proud of herself. And that's very important for me.

"I'm aware that people are always going to have something to say about it. But we are quite clear, and the matter has been spoken about. And all we want to do is really have fun, we are on different paths, and that's great to see."

There was also the suggestion earlier this month that Mabuse had been hired to provide some ethnic diversity to the otherwise white line-up of Strictly judges and presenters.

Pineapple Dance Studios star Louie Spence told The Daily Mirror: "They've got somebody of colour, which is being diverse. They like to tick every box. I'm not saying she's not credible, but maybe that's why they chose her... There's all the boxes that have to be ticked now, the box for the gay, the box for the lesbian, the box for the black, the box for Asian."

But, speaking to journalists earlier this week, the BBC's entertainment controller Kate Phillips said Mabuse had got the job purely on merit.

"We spent a long time talking to a lot of talent from the dance world, screening a lot of people, and it's the honest truth that when we saw Motsi's screen test we were all just blown away," she said.

"And the simple reason we picked her is she was the best person for the job. That screen test combined with her already good judging and dancing credentials made it a no brainer."

Image copyright Getty Images Image caption This year's contestants attended the red carpet launch on Monday

Mabuse says she's excited to get started, and is looking forward to working with this year's crop of celebrities - despite accusations that the line-up isn't as starry as it has been in previous years.

"I think it's good, because of its variety," she says. "They've got different people from different walks of life, which attracts different audiences.

"You have some YouTubers [Saffron Barker is this year's Joe Sugg], which maybe the older generation don't know, you have Karim [Zeroual, CBBC presenter] for the kids, and then you have the sport guys [James Cracknell, Alex Scott, David James, Will Bayley, Mike Bushell].

"It's really mixing things a little bit up. And it's a bit of a show of our times, which I think is really good. Because we have different worlds and ages coming together now, and it's representative."