Carolyn Mayling’s vivacious daughter Rosie was just 11 when she died suddenly in May 2003. “Mummy, I am going to die of this,” she had declared fearfully the previous December when she couldn’t stop coughing. Carolyn reassured her daughter everything would be fine. After all, she had so much to look forward to, having just started pantomime rehearsals at the theatre school Carolyn runs with her sister.

“She managed a couple of weeks of rehearsals before she had to drop out of the show,” remembers Carolyn, whose former pupils include Kate Winslet, Joanne Froggatt and EastEnder Lucy Benjamin.

“Rosie struggled through Christmas Day, trying so hard to enjoy herself. She had lost weight, had no energy, and the dark rings under her eyes gave her a gaunt look. Even though medics were not concerned, my husband David and I had a deep sense of unease.”

It wasn’t until April that Rosie was finally diagnosed with vasculitis – an auto-immune disorder which causes the blood vessels to become inflamed.

It was not supposed to be a serious illness, and can be treatable, but Rosie continued to deteriorate.

Then in early March after a CT scan, Rosie was suddenly taken into hospital. She spent six weeks on heavy medication and was eventually discharged, but was home for just six days before suffering a haemorrhage followed by a cardiac arrest.

Rushed back to hospital, she was placed on a ventilator for nine days before it was finally switched off on May 14, 2003, after doctors revealed there was no hope. It was a devastating moment.

“We didn’t have a clue how to survive the catastrophe which had just befallen us,” says Carolyn, now 68, whose elder daughter Ellie was 14 at the time. “How were we to look after Ellie and survive in this world when Rosie was no longer in it?”

The home she shared with her then-husband felt unspeakably quiet as Ellie pined for her younger sister. The two girls used to love putting on little plays and performances. “They had been soulmates, they were inseparable,” recalls Carolyn, her voice barely a whisper. After Rosie died, Ellie put all their toys away and stopped singing.

“There was this awful silence,” Carolyn adds, remembering how she watched Ellie learn to live alone.

“I couldn’t bear the silence. I couldn’t bear the nothingness; the void.”

In the hugely-affecting memoir she has now written about losing Rosie and finding new life, Carolyn describes “despair of the greatest magnitude” – revealing that her single reason for getting through each day was to care for Ellie.

Reeling from the devastation of all that had been lost, she was in her mother’s garden in August of that year, when she heard a forthright little voice in her head.

“It was Rosie’s voice, and she was saying ‘Don’t talk about it. Do it!’. This was her favourite saying,” recalls Carolyn.

She could see the image of a baby in her head. The vision persisted for days.

“I realised that, somehow, I had retained the capacity to think of loving another child,” she says today. “At first, I was so shocked I couldn’t mention it to anybody, particularly David.

“It felt like betraying our beloved daughter by even entertaining the thought of having another child. Rosie’s death had broken his heart, she was not replaceable.”

Carolyn’s mother also told her in no uncertain terms that the idea of having another baby at her age – Carolyn was then 49 – was “crackers”.

So she put the thoughts to one side until the following Spring when she read a book by the mother of Sarah Payne, the young girl murdered by paedophile Roy Whiting in 2000.

Sarah’s mother later went on to give birth to another child.

“In the last paragraph, she wrote that, although the new baby could never replace Sarah, it ‘gave her back a tomorrow’,” Carolyn explains. “I felt we too deserved a tomorrow.

“If a new life could bring us back into the now, surely, this was better than not having anything at all?

“But whoever in their right mind gave birth to a baby at 49 years old? What planet was I on?”

In fact, Carolyn was 54 when her son, Dominic, now 14, was born after IVF using a donor egg in December 2008, five years after Rosie’s death.

His arrival offered everything Carolyn had dared to hope for. This robust teenager is even happy to endorse the book his mother has written about his unique genesis, and to take part in the Daily Express photoshoot to promote it.

“It’s cool Mum has written the book, and of course I’m proud of her,” Dominic says.

“I’ve known all my life about how I came to be born. The fact she had a vision from Rosie is just Mum being Mum.”

Carolyn says she has always been open with Dominic about his history. Now he’s intrigued to find who his egg donor was.

“Yes, I might want to do that,” he continues. “Mum says, when I’m a bit older, I can see if I can find out.”

When Carolyn first approached her GP for treatment and was referred to a fertility clinic in Windsor, she was told that, due to her age, she would require a donor egg. She then went to visit a spirit medium, who confirmed there would indeed be another child – a boy – on the way soon.And still, Rosie’s persistent voice in her head was telling her to “just do it”.

“All the time, I felt it had been preordained,” Carolyn recalls. “Everything was compelling me to go forward.”

Initially, her sister Sam offered to be her donor.

“I had two cycles with my sister’s eggs, but both failed,” says Carolyn.

“It was really gutting, especially when I hit 50 and the clinic told me they couldn’t treat me anymore.”

It was then that she turned to a fertility clinic in Harley Street. Although they had a three-year waiting list for treatment in London, they told Carolyn and David about their sister hospital in Cyprus where things would move a lot more quickly.

In April 2008, the couple flew to Cyprus for the egg transfer, using an egg from a donor in Moldova. “When we got to Cyprus, it was Easter and there were giant, 100ft-tall eggs everywhere,” laughs Carolyn. “It felt like a sign.” Eleven days later, a pregnancy test confirmed that she was expecting their miracle baby.

“After that, it was a completely normal pregnancy,” she says.

Dexpite her earlier concernt, Carolyn’s mother, now 92 years old, dotes on her only grandson. “Grandma June thinks he’s wonderful and is immensely proud of him,” says Carolyn.

“After all, her other 10 grandchildren are all girls.”

Ellie also adores her little brother. Carolyn adds: “She found it difficult at the beginning, but by the time we went to Cyprus, she was really behind the idea. She was 19 by the time I was pregnant with Dominic, and busy with her own life.”

David and Carolyn had separated but they remain amicable co-parents.

“You’ve got to have a very strong marriage to weather the loss of a child, and the strain on us both was just too much. We grieved in different ways. But we have a good working friendship.”

In 2004, Carolyn set up a charity called Rosies Rainbow Fund to help other parents of desperately ill children.

Its patron is Lucy Benjamin, the actress who found fame as Lisa Fowler in EastEnders, and who won X Factor: Battle of the Stars in 2006. Lucy had attended the same drama college as Rosie, Redroofs Theatre School, which had originally been set up by Rosie’s grandmother.

“When Rosie died I wanted to create a legacy in her honour,” says Carolyn.

“Rosie was in hospital when she said we should help other families.”

The charity now has a team of music therapists who work in hospitals, as well as helping parents most in need. When Lucy won X Factor: Battle of the Stars, she donated all her prize money to Rosies Rainbow Fund. Other game-show winnings were donated too.

“And when she was pregnant with her youngest daughter, she told me that she planned to call her Rosie,” Carolyn explains. “It was so touching.”

Lucy’s own Rosie is now 11 years old – the age that Carolyn’s Rosie had been when she died. As for Dominic, he says he never worries about his mum being older than his friends’ parents: “She’s just like my friends’ mums.”

Carolyn adds: “I do occasionally think about how old I will be when he’s 30, but he’s a pretty well-adjusted boy and takes it all in his stride.”

She and Dominic moved house last year. Carolyn was finally able to offload boxes of Rosie’s clothes which had been frozen in time for 18 years.

She says Dominic will occasionally ask her for more information about Rosie.

“I readily share it and he enjoys hearing about it,” Carolyn says.

“But only in small doses before he turns his attention back to his Xbox or asking what’s for tea.”

• The Future is Rosie by Carolyn Mayling (Alliance Publishing Press, £11.99) is available via Amazon and to order from all bookshops. For more information about Carolyn’s charity, visit rosiesrainbowfund.co.uk