The Grease star opened up about her Welsh father Brinley's role in World War II during her appearance on The One Show, but admitted she didn't know the whole story about his time at Bletchley Park, which served as Britain's secret intelligence headquarters.
She said: "He was part of the team that cracked the code, Hitler's code. He was at Bletchley Park and he was a wing commander in the Air Force and he spoke perfect German, so they used him to interrogate the German prisoners of war. But he couldn't talk about it so I didn't really know much about it."
Newton-John was thrilled when the hosts then introduced a Bletchley Park employee named Ian, who explained how Brinley turned deciphered messages into intelligence which was sent to commanders in the field.
Ian also revealed: "He was a major player in the Amateur Dramatic and Operatic Society... I think he was also probably quite a dashing chap, because (in) a production of Pride And Prejudice, he actually played the dashing Mr. Darcy."
The singer/actress was then treated to a clip of her dad performing an aria from The Marriage of Figaro, in which he played The Count.
An emotional Newton-John said: "You know why this is really amazing? Yesterday was his 99th birthday, so it's perfect you should tell me this today... Thank you! He had a beautiful voice, so I thank him for some of the genes he gave me!"