Vicky McClure goes on an emotional journey to Taiwan to find out what happened when her great-grandfather was captured as a prisoner of war in World War Two

Certainly not the BBC. Although its executives anticipated a little interest in Who Do You Think You Are? when the first series hit our screens in 2004, they didn’t foresee large audience figures, public acclaim and the desire for more.

That opening run featured the likes of Vic Reeves, Jeremy Clarkson, Amanda Redman and Bill Oddie, while the second focused on such luminaries as Sheila Hancock, Julian Clary and, best of all, a particularly moving insight into the family of Stephen Fry. Both seasons were scheduled on BBC Two, but their popularity led to the show moving to BBC One for its third series – where it’s stayed ever since.

As is often the case with a hit, the format has since been sold around the world, with versions popping up in Poland, Australia, Germany, Ireland, the US, France and South Africa, among others. Rival broadcasters have also attempted to launch similarly themed shows, including My Famous Family, which aired on what is now the Yesterday channel, and ITV’s DNA Journey and You Don’t Know You’re Born.

After such a long time on our screens, whenever a new series is announced, viewers wonder if the show has run out of big names to investigate. However, we’re pleased to announce that researchers have pulled out all the stops to create a wonderful 21st season to help the show celebrate its 20th year.

It promises to be a globe-trotting affair too, with trips to Ireland, Taiwan and Jamaica on the horizon. For actress, disability rights campaigner and Strictly Come Dancing superstar Rose Ayling-Ellis, matters remain more grounded – she investigates exploits in a Birmingham pub.

Presenter and comedian Paddy McGuinness also learns about a family member’s exploits during the Second World War, while pop star Olly Murs discovers that entertainment runs in his blood – he has ancestors who were circus performers.

Spice Girl Mel C explores how her relatives escaped a devastating famine, Olympian Jessica Ennis-Hill learns about an enslaved ancestor who went on to own land, and reality TV star Gemma Collins meets a family member she never knew she had while uncovering how deep her Essex roots really lie.

But first up is Line of Duty star Vicky McClure. Her personal journey takes in 6,000 miles of travel while she delves into the emotional stories of her paternal grandmother and maternal great-grandfather. She wants to know why the former was given up by her biological family, and what happened to the latter after he became a PoW.

“This year we have a stellar line-up to mark 20 years of the nation’s favourite social history series,” says Simon Young, the BBC’s Head of History. “Time and again it proves the old adage that truth is stranger than fiction, while helping us all to understand the history of Britain and the world much better.

“I’m so grateful to all the celebrities who have shared their family histories, and to the incredible production team that pulls it all together.”