Hayley Mills soared to stardom as a child actress under Walt Disney's guidance for seven years - only to watch her once-considerable earnings disappear. She confessed that a "rather big chunk" was lost due to a "super tax" of 90%.

The star, best known for her performances in Pollyanna and The Parent Trap, recently joined her sister, Juliet Mills, on The Rosebud Podcast. The appearance marked Hayley's 80th birthday celebration. When presenter Gyles Brandreth questioned the former child actor about what happened to "the millions" that she accumulated during her Disney period. She responded: "I gave it to the tax man. It was rather a big chunk. It was most of it because it was all put into a trust fund, because the super tax was 90% in those days, so they had to do something."

"I do know the background of this, and it's partly because you were poorly advised," said Gyles. "But also, it was partly to do with the naïveté of your father, I think. There was an innocence about him and a sort of optimism." Juliet, 84, chimed in, adding: "He had a business manager who made those sorts of decisions."

The Mills sisters hail from a distinguished British acting dynasty. Their father, Sir John Mills, was among Britain's most esteemed actors and enjoyed a career spanning several decades. Their mother, Mary Hayley Bell, was also an actress and playwright.

"Stanley [Passmore] also advised Daddy, and not very well," said Hayley, referring to the family's solicitor. "The trust company was set up for me. Stanley was also involved in setting up a trust company for [actor] Jack Hawkins. And the Inland Revenue attacked his trust company, which affected British law. It created the precedent.

"And so, when I reached 21, instead of being given the key to the door, I was handed an envelope across a green baize tablecloth by Stanley, which was the Inland Revenue basically saying, 'Thank you. You owe us 90% of your earnings,'" she continued. "And I've never been good at figures.

"I said, 'Well, what does this mean? I don't understand.' And Stanley laughed and said, 'Well, I think it means you have to move to America [for work].' And that's all he ever said. He was a crook. He didn't give a flying Dutchman."

Speaking on the podcast, Hayley recalled seeking counsel from a prominent lawyer in a bid to contest the matter, but "it didn't work." Lord Denning, one of Britain's most formidable judges of the era, briefly handed the actress a victory in her battle with the tax authorities. During the 1970s, he ruled in her favour, concluding that the manner in which the government had taxed her Disney earnings was unjust.

However, the triumph was short-lived. The case was taken to the House of Lords, which overturned Lord Denning's ruling, leaving Hayley liable for the enormous bill that stripped away much of her wealth.

She lobbied the British government for years, according to reports. Yet her appeal was definitively rejected in 1975. Had she prevailed, Hayley claimed she would have been able to retain approximately £2 million, equivalent to well over £17 million in today's money.

"I didn't have a sensible enough sense of my career and what I ought to be doing, but I didn't want to do more Disney movies," said Hayley. "I wanted to spread my wings and have a greater choice and not be limited by that.

"[But] I didn't know what to look for. I didn't know who I was. There was this moment when we were growing up when we were really on that uncomfortable seesaw, one foot in childhood and the other in being a woman.

"And I found it awfully difficult to get both feet into womanhood because there was a part of me that didn't want to disappoint people. 'Oh, she's not that cute little girl anymore.

"She's what?' I didn't know what sort of thing to look for."

Following her transition into motherhood, Hayley pursued stage work and secured several television roles in the US. She continues to act on occasion.