Jodie Whittaker discovers surprising secret about her great-grandad in "heartbreaking" Who Do You Think You Are? episode

One of the secrets is about her great-grandad - or should we say the man she believed to be her great-granddad.

In the episode, Whittaker shows her mother a photo of five brothers during the 1920s.

As she points to a man in the centre, she says: "I was convinced that's my great-granddad" to which her mother responds: "You are wrong," causing the actress to burst out laughing.

The misunderstanding is cleared up, as her mother informs her that her great granddad is Edwin Auckland, who is on the end of the photo and the other man would have been her great uncle.

There are some parts of Whittaker's history, however, that she struggles to come to terms with.

During the episode, she learns that her great grandmother on her dad's side, Eliza, had an illegitimate son named Walter when she was in her teens.

Eliza left Walter behind when he was just seven-years-old to move to London with her new husband, George Bedford.

The pair ended up having eight children together.

Whittaker "suspected" there was something up when she first read the children's names and saw that Eliza's second child was named after George, not Walter.

"It's just that idea of a little kid being left that's slightly heartbreaking," Whittaker proclaimed, as she added: "I wonder if she [Eliza] saw him again."

Whittaker's worry led her to investigate further into Walter's life, only to discover he died at war when he was 24-years-old, and was buried at the East Finchley Cemetery - which happens to be the same graveyard George Bedford worked at as a grave digger.

This piece of information almost brought her to tears as she believes this would have been the moment Eliza was reunited with her first born child.

Reading his birthstone, which lists Eliza as his mother, seemed to confirm this for her.

"It feels like there's been an involvement here from Eliza that she knew he was in that hospital and she got to bring him back to her home and for the rest of her life. It's so upsetting!" she said, trying to keep her composure.

"She has her nine children around her and for those other children, they've got this place to come to and celebrate this little life."

"Desperate" to see Walter's grave, Whittaker takes a visit during the episode, and it dawns on her that the only time Eliza and Walter would have been back in the same place since he was a child would have been when he passed.

This realisation leaves the actress feeling conflicted, as she says: "The only time Eliza and Walter were physically this close was in death, and it's just incredibly sad and feels unfair!"

Jodie Whittaker's Who Do You Think You Are? episode is on BBC One on October 12th at 9pm. Check out what else is on with our TV Guide.