Claudia Winkleman, Mika and Jon Batiste on The Piano – and the stories that stay with them

Her flared trousers extend over her shoes, giving the impression that she's gliding on tiny wheels around the huge Glasshouse International Centre for Music in Gateshead, like Doctor Who's Davros or the robot Metal Mickey. She is, it ought to be said, measurably less terrifying than the former, and slightly shinier than the latter.

"You might wonder, throughout the course of today, whether I do anything other than hand out sweets and biscuits. And the answer is, very little." Winkleman then links arms with me and pulls me over to a partitioned section where New Orleans piano polymath Jon Batiste and chart-topping pop star Mika are seated. "Have you met my little brothers?" she beams.

The mood is celebratory and with good reason. Three years after first appearing on our screens, The Piano continues to defy the downturn in viewer demand for talent contests. Five weeks ago, over 2.5 million viewers tuned in to watch Mika and Batiste (who replaced outgoing mentor Lang Lang) gaze on from their secret vantage point as seven amateur pianists walked across the concourse at London’s Liverpool Street station to share their stories.

That’s an increase of over half a million viewers on the number who watched the beginning of series two, which saw 23-year-old Liverpudlian Brad Kella ink a record deal on the back of an original composition dedicated to his foster parents, Eve and Frank.

Viewers tuning into the finale of series three will no doubt be rooting for the pianist they want to see go on to similar success. Could it be Zak from Chapeltown in Leeds – known for its history of social deprivation and race riots – who likes to play in the key of C sharp minor because, "that’s what it feels like to live around here". Or perhaps teenage Mia, who said she had googled ‘black, female composers’ because, "no one else who looked like me seemed to be [playing classical piano]". Or the equally extraordinary Diana, who at 87, premiered her first composition, written in memory of Phil, her husband of 63 years who died of Parkinson’s?

And, of course, sometimes it’s fine not to have a back story – such as the pianist last year who, when asked, "Has the piano ever helped you through a difficult time in your life?" replied, "No".

By contrast Mika and Batiste’s connection to the show is inextricably bound to their formative experiences with the instrument. The Mika of 20 years ago was, by his own admission, a very different creature. Born Michael Penniman, in Beirut, to an American father and Lebanese mother, he spent his earliest years in Paris, before a move to London precipitated "a little breakdown" and a period of elective mutism during which he stopped talking altogether.

Oddly, as a chronically shy child born into a New Orleans musical dynasty, Batiste went through a similar period of self-imposed silence. When this is pointed out to them, they both turn to face each other in amazement. "I didn’t know that about you!" gasps Mika. "Well look at that!" purrs Batiste. "So, what happened to you?"

"It was a combination. I went to this school [the Lycée Français Charles de Gaulle, a west-London state school for the children of French expatriates]," explains Mika. "And then the homophobic bullying started, and it was just… At a certain point, you say, ‘What’s the point? I only make things worse when I open my mouth’. And it’s just not true, but it’s what you think. And you?"

"There was a lot happening internally," recalls Batiste, "I felt like I was observing the world up until that point, as opposed to living in it. But when I finally discovered the piano, I became a performer."

For Mika, the transformative power of the piano isn’t just a theory. Smarting from a series of record company rejections, he sat at the keyboard and practically throttled his debut single Grace Kelly out of it (Sample lyric: "Why don’t you like me, why don’t you like me?") in the process topping the charts for five weeks in 2007. If The Piano had existed at that time, he says he would have played either that song or something from Harry Nilsson’s 1967 album Pandemonium Shadow Show – an album that sounds like a 1960s prototype for everything that Mika has gone on to do. Batiste plumps for Labi Siffre’s somewhat less angry My Song, a plea for the wider world to find a place for its protagonist’s gifts.

All of which leaves Claudia to reveal what she would play. There’s 20-year-old pre-fame, pre-fringe Claudia standing before the piano that can launch her into the affections of the viewing public… "You know I can’t play, right?" she asks. I wave an imaginary magic wand. She can now. "I can’t sing either," she replies. I wave it a second time and warn her that she has one wish remaining.

"OK. It would be As by Stevie Wonder. Because it would speak of the family that I hoped to have, and the family that I went on to have and how everything else is… croutons."

Batiste slaps his thigh with delight: "You’re speaking, Claude! See how she does that? It’s like she gives veteran icon energy. Anything you say, she can come with a witty response. How do you do that? What is that?"

"I’m 52," responds Claudia with deadpan severity, before turning to face me. "You’re sticking around for the show, right?"

Three hours later, several hundred pairs of tear ducts are once again sent into overdrive as the full extent of Mika and Jon Batiste’s mentoring sessions with this year’s finalists is revealed. One person who seems to remain resolutely unmoved, however, is the presenter of the show. How on earth does Claudia’s mascara manage to defy the emotional whirlwind happening around her?

"Because when somebody’s telling you their story and the power of it is overwhelming, my job is to give them some strength and safety. After my dad watched last year’s final, he phoned me up in tears and he said, ‘That is by far the best thing you have ever done’. And that’s enough for me, because I can never watch anything I’ve done back."

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The Piano is available to watch on Channel 4.

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