Yet, while her parents were open about the fact she’d been adopted, they chose to conceal the true nature of her parentage for her own protection.
When asked, her parents told her that while her birth mother lived in France, and that she had a grandmother who lived in London, they said they didn’t know who her biological father was.
A kindly brigadier and his wife, they raised her alongside their son Colin Thubron, now a respected travel writer, at their idyllic country home in Uckfield, East Sussex.
It was a world away from the sun-drenched Los Angeles mansion where Rod now spends much of his time, but Sarah, who works in a care-home, was wonderfully happy there.
Understandably, it was a profound shock when, at 18, Sarah discovered that the singer whose poster adorned her bedroom wall was in fact her father.‘It really didn’t sink in to start with,’ she says.
‘I just didn’t want to lose her, and my whole world just fell apart after she died,’ she says.
‘I didn’t realise until she died how dependent I was on her.
Susannah, initially, wanted to keep the child, even though Rod had told her he was too young to have a baby.
After Sarah was born, he asked her to give the baby away and, after she refused, the couple split up.