Mara Wilson shot to fame when she was just six years old, starring alongside Sally Field and Robin Williams in Mrs Doubtfire.

She later landed the role of Susan Walker in Miracle on 34th Street, before finding acclaim as Matilda Wormwood in the film adaptation of Roald Dahl’s beloved book.

But, after puberty, Wilson all but disappeared from the public eye.

And now, speaking in her upcoming book, Where Am I Now: Stories of Girlhood and Accidental Fame, Wilson has explained that this decision was made after she was subjected to the dark side of life as a child star.

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In extracts from the book, published in The Guardian, Wilson recalled an incident where she was sat down by Britt Allcroft, the director of Thomas and the Magic Railroad.

At the time, she was told that she was now a “grownup 12-year-old” and, as such, would need to start wearing a sports bra – a comment which left Wilson feeling “alienated” from her own body.

Shortly after this incident, the young actress looked herself up on the internet – and was horrified by what she found.

“A website called Mr Cranky wrote that I was popping up in every movie these days because I would soon be entering ‘the awkward years, when she’ll be old enough to have breasts, but not old enough to show them legally’,” she recalled.

“I folded my arms over my chest just reading that, and even as an adult it makes me shudder. Who did they think they were, talking about a preteen girl’s breasts?”

Wilson went on to reveal that she “burst into tears” when she clicked onto the next page of search results, which featured a website proclaiming to have “nude and sex pictures” of her.

She explained that, at the time, she struggled to comprehend what she was seeing – and she even wondered if she had been drugged and kidnapped to create the images.

“Some rational part of my brain remembered that there was such a thing as photo manipulation, that they could put my head on someone else’s body,” said Wilson.

“But that didn’t make me feel any better: who was this poor anonymous girl whose body stood in for mine?”

It was only the beginning; Wilson went on to find herself featured on a foot fetish website that catalogued the feet of child stars, and received a number of strange and unseemly requests from adult fans.

“There was even a rumour on IMDb that I had died from a broken neck,” she said.

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Wilson added that her status as a “cute” child star went on to affect her self-esteem, particularly as she grew up.

She found herself being bullied by her peers, having her weight constantly commented on, and unable to get call-backs at auditions.

When she was told that she could play the ‘fat kid’ in a new television show, despite the fact that she had wanted to play the “neurotic” character, she quickly realised what had happened.

“Things had changed,” she said. “At 13, being pretty mattered – and not just in the world of movies and TV.

“The pretty girls at school had always had an air of superiority, but once we hit puberty, they seemed to matter more. My career was the only thing I had over them.

“Now that it was waning, I was just another weird, nerdy, loud girl with bad teeth and bad hair, whose bra strap was always showing.”

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Wilson eventually chose to put her schooling above her acting career, and watched many of her child actor peers – such as Kristen Stewart and Scarlett Johansson – grow up and become “sexy” women.

Nowadays Wilson is a playwright and comedy writer and she’s dipping her toe back into the world of showbiz again by voicing a character in the animated series, BoJack Horseman.

And, if anyone questions her decisions, or comments on her looks, she has already planned the perfect response for them.

“I will tell them how fitting it is that the only real acting I do these days is voiceover, where no one can see me.

“I will tell them how my [late] mother wanted me to prove myself through my actions and skills, rather than my looks. Now I believe I have, and I am happier than ever.”

Earlier this year, Wilson was praised for coming out as bisexual following the massacre in Orlando, which saw 49 people gunned down in gay club Pulse.

Sharing a photo of herself at a gay club when she was a teenager, she wrote: “Me at a gay club when I was eighteen.

“I feel embarrassed looking at it now… being a ‘straight girl’ where I clearly didn’t belong, but I will say, I felt so welcomed.”

“I have never had a better experience at a club than I did then. Great music and people. And one of my friends met his partner that night!”

She continued: “But the LGBTQ community has always felt like home, especially a few years later when I, uh, learned something about myself.

 “I *used* to identify as mostly straight. I’ve embraced the Bi/Queer label lately.”

Where Am I Now: True Stories of Girlhood and Accidental Fame is out on September 22 through Penguin Books.