Rachel Stone was five and her brother Ian was 10 when their mum and dad took them on a caravan holiday to Wales with the family next door.

They spent two fun-filled weeks together – but when they got home, each family split in half and swapped houses.

Rachel and her mother Kay moved in with the neighbour Eddie and his daughter Alison. Eddie’s wife Irene and their daughter Dawn moved in with Rachel’s dad Rex and her brother Ian.

Rachel tells Dr Sian Williams, host of Radio 4’s Life Changing podcast, of the trauma of her family being torn apart, the chaos that unfolded and how she has come to forgive her parents.

Rachel and Ian had initially been delighted when a new family moved in next door. “We instantly hit it off, all four of us.” They were thrilled to be going on holiday together.

Rachel remembers two caravans parked side-by-side and a trip up Mount Snowdon.

But when it was time to go home, everything was mixed up – people were getting in the wrong cars.

Rachel remembers her mum leaning back from the passenger seat, saying: “‘We’re going to have a new family. We’re going to be living in number eight with Eddie and Alison. Alison’s going to be your new sister.

“And your dad and brother are still going to live in number 10. And Auntie Irene and Dawn are going to live there. And Dawn’s going to be your brother’s new sister.”

Rachel immediately felt “very panicked and afraid and upset” and says she started to cry.

As the car rumbled along, she felt “bewildered, but also a little bit excited”. She liked Alison and had always wanted a sister.

That night, Alison let her sleep on her top bunk and the next morning the adults switched belongings between the houses in the Isle of Sheppey where they lived.

Rachel says she felt very confused. “You can’t help but think that it’s your fault.”

Life at number 8, where Rachel now lived, was very different to number 10. Her old house had been clean, whereas this house had “dog hair, greasy things, car things”.

She describes her mum as “firm but fair” and very practical.

Her stepdad Eddie “was never horrible to me, but I never called him dad. I wasn’t his girl.”

She also missed Ian desperately. “I was very proud of him. He was my big brother.

“I used to wait in the front garden for him to come home from school when I was a toddler.”

Rachel was seven when the two couples went to court together and got divorced. They later married their new partners in separate low-key registry office ceremonies.

Rachel did not even know her dad had married Irene until she saw the wedding photo. Her visits to her old home tailed off when she was about 11 or 12. She says she found it difficult to go and visit her dad and did not get along with Irene.

Meanwhile, life with her mum Kay and Eddie was chaotic.

“[He] was quite possessive and controlling. By the time we got to 13, she [Mum] said, ‘it’s not sustainable, [we] can’t live like this”.

Rachel said school was her “escape”. She got good grades and became a teacher. She got married and had two sons but is now separated and works as a business coach.

Throughout her life, Rachel’s mother would never talk about the swap. “I asked a lot of questions. She told me it was complicated.”

Decades later, on a family holiday with her own sons, Rachel asked again.

“I said to my mum, ‘Oh, Joseph’s 10 now… Ian was 10 when you let him go with Dad and Irene.'”

She says her mum was “beside herself with guilt and the shame… for her selfish decisions”

“Years later she actually said to me – the words I almost wanted to hear all my life – ‘I’m so sorry I let you down and I want to try and make it up to you.'”

Rachel says it was the start of her rebuilding a “wonderful” relationship with her mum.

Rachel never had a close relationship with her dad. “He told me he had a choice between his wife and his children. Unfortunately for me, he chose his wife.”

He and Irene stayed together until his death aged 81.

But when she spoke at her dad’s funeral, Rachel said she felt she owed him an apology.

“I imagined a character of a perfect dad that had been taken away from me… I created this superhuman being that could be everything.

“And I wanted him to be like that. But I also think you have to accept people for who they are.

“I think that parents do the best they can… You can’t hope for your parents to be something they’re not.”