WHEN KT Tunstall signed up to Long Lost Family, she understandably had her doubts. The Suddenly I See hitmaker, who had always known she was adopted, grew up in St Andrews, Scotland, in a loving family. But it was – surprisingly – only after watching the Mike Leigh classic Secrets & Lies that she began to think about finding her birth parents.
"I was watching this amazing cast portray that experience," she says of the 1996 film. "I met Brenda Blethyn not long after finding my birth mother and told her about it; she was crying and said, 'I can't believe you did it'.
"Watching someone go through this experience in a real or fictional way can have a profound effect on you," she recalls.
"[But] it's a big decision to make because you basically step through a doorway that you can't go back through again," she warns. "You can't make it unhappen, and you've got to take the risk of finding out whatever and being OK with it."
Fortunately for Tunstall (44), her own search for her birth mother, Carol Ann, paid off. And having successfully tracked her down in 1998, the pair have since formed a good relationship. However, the whereabouts of her biological father remained a mystery.
That was until Long Lost Family – the Bafta-winning ITV series – stepped in. Now in its ninth season, the tearjerker – presented by Davina McCall and Nicky Campbell – has traced hundreds of missing relatives since its inception in 2011, with the help of trained intermediaries, DNA experts and investigators from all over the world.
Tunstall, however, was its first celebrity searcher. And her decision to participate in an episode of the show's latest seven-part run was not taken lightly.
"I needed to have a think about whether I want to do it on camera," she says. "I haven't really watched telly since about the year 2000, so I wasn't aware of these kinds of real-life programmes.
"And obviously the worry is 'What's the agenda here?' Are they wanting some sort of salacious, crazy, Jeremy-Kyle style nightmare scenario that is going to get everyone watching?
"But it became apparent very quickly that this was a very emotionally mature, very experienced team, who literally just want to find family members and put them together in the safest and most positive way.
"After I realised that, it was like, 'Yeah, no brainer!'" she says. "Finding my birth mum was hard on my own, whereas this is a team of researchers with tonnes of experience and access to stuff that I'll never have.
"Also there's amazing psychological and emotional support and I wish I'd had that the first time around," she says. "And when it came to the public side of it, it was like, 'Well, there's lots of adopted people who aren't sure about whether they want to do this, and hopefully by doing this, [it will help]'.
"Apart from anything else it's a very emotional, human story, and those things are positive to share."
So how much did she know about her birth father to begin with?
"I probably had a bit more information than you usually would – I knew his name, I knew that he was from Northern Ireland, I knew that he ended up living in northern Scotland," she says.
"And then, when I met my biological mother, she told me a bit more about him as well; she's always said that he's a good person, with a good heart...
"She told me straight off the bat that he wanted to get married and keep me and be my father, but she was just not able to do that," she adds. "So, she was really pleased that I was going to find out about him; I think she thought I would have had a chance to meet him."
Sadly, it wasn't meant to be, however, as Tunstall discovered during the making of the show that her dad, John Corrigan, died in 2002.
"He died quite young – but he'd gone on to have children with a new partner very soon after I was born," she says. "My two sisters [Siobhan and Lesley-Anne] were growing up about 35 miles away from me!"
They've since met: "We look like each other, which is absolutely bonkers for all of us," Tunstall says excitedly.
"I can't imagine what it's like for them, because I knew there was always a possibility that I had half-siblings in the world but they had no idea," she muses, the siblings having been a fan of the singer – buying her album and seeing her play at festivals – unknowingly.
Doe she feel a sense of closure?
"It just feels like there's been a missing corner of my painting, of who I am," she says. "I've got four parents, and three of them, I've known what they look like, I've known who they are. And then that fourth corner was basically a complete blank."
"But I wasn't walking around feeling lost..." Tunstall is quick to add, the Brit Award winner confirming that her adoptive parents have always been "enormously supportive".
"Had I gone to my grave not knowing, I wouldn't have suffered because of that," she states. "But I definitely feel that I will now have an enriched life, certainly, from knowing my sisters."
She hopes that sharing her story will also enable other adoptees to take a leap of faith.
"It takes courage to ask the question, because you don't know what you're going to get," she says. "You could get a disturbing story that you've got to live with for the rest of your life, I was extremely lucky."
Now Tunstall, who has just finished touring the UK, Europe and the USA, is about to start the UK summer festival circuit – including an intimate gig at St Malachy's Church, Castlewellan, later this month, as part of the Co Down town's annual Soma festival.
"We've got loads of festivals – and I'm also actually going to Japan and China as well!" reveals the singer-songwriter, who kicked off her music career with debut album Eye To The Telescope in 2004.
As for new music: "I don't write very much when I'm on tour," she says. "It's kind of all-consuming, but I'm making a new record this autumn and it's the final in a trilogy of records about soul, body and mind.
"I've done the soul one and the body one," she finishes. "And the mind one will be out next year hopefully!"
:: KT Tunstall plays the Soma festival, Castlewellan, Co Down, on July 17; for information and tickets see somafestival.com. Long Lost Family is on ITV, Mondays; See her episode at itv.com/hub/itv
