Nicki Chapman has revealed she underwent surgery for a brain tumour "the size of a golf ball" and told doctors not to resuscitate her if anything went wrong during the operation.
The TV presenter will not present this year's RHS Chelsea Flower Show for the first time in more than a decade while she recuperates.
She told Saturday's Daily Mail: "You have to give yourself the best possible chance to heal, so I won't be presenting the Chelsea Flower Show this year.
"You start at 5am and it's five 12-hour days, and I don't think I could manage that yet. I'm devastated. I watched the preview and it made me cry.
"I've done it since 2006 and, of all the shows I present, it's the one I really regret not being able to do. But I have to follow my doctor's advice. You don't get a second chance to recover."
The 52-year-old, also known for presenting Escape To The Country, said the diagnosis was the "worst news I've ever had in my life", but that she tried to remain positive.
She said: "It was the worst news I've ever had in my life, but I thought 'We're going to find a way through it'. And I really hope that other people who get a similar diagnosis have the excellent treatment I had, and find the same inner strength."
Talking about her symptoms, which she said included a change in her vision and speech as well as memory lapses, she said: "I went to do a voice-over for Escape To The Country and I couldn't remember the name of John, the executive producer. I've known him for 15 years. I had to look it up on my phone."
Doctors told her she had a tumour on the back, left-hand side of her head, which was "the size of a golf ball pressing on my brain", she told the paper.
Morning. This is why I've been off social media for a while. Thank you Frances Hardy for a wonderful and sensitive interview. I hope this story may help others going through something similar. 'I had a brain tumour the size of a golf ball': Nicki Chapman https://t.co/1c1ZWrE4t6
- Nicki Chapman (@Nicki_Chapman) May 18, 2019
The former Pop Idol and Popstars judge did not want to be resuscitated if complications arose during the operation.
She said: "They'd said I could suffer a bleed on the brain during the surgery and I'd told him 'If anything goes wrong, I don't want to be resuscitated and come back in a body I can't use'."
Sarah Lindsell, chief executive of The Brain Tumour Charity, said: "Our thoughts are with Nicki Chapman as she continues her recovery from brain tumour surgery.
"We're immensely grateful to her for speaking out about her diagnosis and its impact.
"Nicki's decision to share her experience will make a real difference in helping to end the isolation felt by so many people who are diagnosed with a brain tumour."
The charity tweeted Chapman saying: "Sending our best wishes to @Nicki_Chapman who shared today that she underwent surgery just 10 days ago to remove a brain tumour the size of a golf ball. "
She replied: "Thank you so much. Let's stay in touch."
:: The RHS Chelsea Flower Show airs on BBC Two.