Who Do You Think You Are? (BBC1, 8pm)

NORTH-EAST star Cheryl is a huge fan of the British military – in 2011 she flew out to visit troops in Afghanistan, arriving at Camp Bastion in the Helmand province to mark ten years of British operations in the country.

At the time she said: "I always had admiration for what the guys do out here, but seeing them here at work is awe-inspiring. I'm delighted to be here to recognise all the hard work they do. Every one of them is a hero in my book."

And her words will hold particular resonance now she knows that she is directly descended from a hero of the Great War.

The former Girls Aloud star, 33, was approached by producers of Who Do You Think You Are? after admitting in an interview last year that she'd love to take part in the family history show. On her mother's side, she learns the story of her long-forgotten great-grandfather, a soldier in the First World War who fought in one of the most famous battles on the Western Front. Joseph Ridley survived the bloody 1916 Battle of the Somme, but was later spurned by his family and considered "the black sheep of the family" for having two children with his housekeeper following the death of his wife.

There are more surprises in store as it is revealed that Mr Ridley was not only a relation of the Girls Aloud star, but also of a another character who has appeared in the media in recent years. Mr Ridley is the grandfather of Yvonne Ridley, the 58-year-old news reporter who was captured by the brutal Taliban regime in Afghanistan in 2001.

Yvonne's father is one of the seven children Joseph had with his first wife, while Cheryl's great-great-grandmother is one of the twins born during the relationship he later had with the housekeeper.

It means the two women, who have never met, are distant cousins. Yvonne has said she was surprised to learn she is related to Cheryl, but added that her daughter looks just like the popstar. "I happen to think she's a great ambassador for the North-East and will enjoy watching her uncover the family tree," Yvonne said recently.

Also during tonight's programme Cheryl says she believes that she has some roots in South America, and undergoes a DNA test to prove whether her hunch is right or not.

She discovers twins run in her family on the show, alongside the rumours that she might be pregnant by boyfriend, One Direction star Liam Payne.

Blue Peter: It's Christmas! (CBBC, 5pm)

THE festive season has always been big news for the Blue Peter team. Older ones can probably still remember how to make a Christingle after watching John Noakes & Co get busy with the glue and tinsel for years. The show's Christmas edition is rather more slick these days, and this year will feature Lindsey Russell turning on the Festival of Lights at Longleat, the cast of Shrek the Musical and Iggy the guide dog. Plus, Radzi Chinyanganya and Barney Harwood attempt to break a world record before the Salvation Army a children's choir sing a carol.

Extraordinary Weddings (ITV, 9pm)

THIS week's moving episode begins with the story of Will and Amy from Cheltenham. A year into their relationship, Will suffered a bleed on the brain that affected his memory. He now struggles to retain new and short term memories, including when he proposed to Amy. However, she is determined that he should remember their big day, and has spent hours finding ways to train her fiance's brain. And then there's Karen and Ian from Scunthorpe. Three years after they met she suffered a stroke that impacted on her voice; she was just 46. Now she struggles to find the right words to form full sentences, and after Ian proposed, they have worked tirelessly in the hope that Karen will be able to say her all-important wedding vows.

Viv Hardwick