The mother of murdered schoolgirl Sarah Payne was in a "life-threatening condition" today after being rushed to hospital with complications after brain surgery.
But a family source said that Mrs Payne has responded well to treatment . He said: "The early signs of her treatment were positive.''
Child protection campaigner Sara Payne, 40, fell ill yesterday. Family members originally intended to keep her plight private until after the Christmas period.
Friend Michele Elliott, founder and director of campaign group Kidscape, said: "Sara is the most wonderful and indomitable person and if anyone can get through this, it's her.
"Everyone needs to pray and send their good thoughts at this difficult time. I have been in tears."
Relatives and friends, including fellow campaigner Shy Keenan, have been at her hospital bedside, she said.
Mrs Payne had a life-saving operation to cure a ruptured aneurysm last year, friends said.
The head nurse at St George's Hospital, in Tooting, south London, where she is believed to be receiving treatment after suffering complications, was unable to confirm her condition this morning.
Since the death of her daughter Sarah at the hands of paedophile Roy Whiting in 2000, Mrs Payne has become a prominent campaigner for victims' rights.
She took up the Government-appointed post of Victims' Champion at the end of January.
Mrs Payne launched a high-profile campaign for "Sarah's Law" after her daughter's murder, giving parents the right to know if paedophiles live near them.
A limited form of the law, based on America's Megan's Law, was announced in February last year.
She was given an MBE for her tireless work to keep children safe from paedophiles in the 2008 New Year Honours List.
Her daughters Charlotte, 15, and Ellie, five, are being looked after by relatives over Christmas. Her sons Lee and Luke are 22 and 21.
Mrs Payne's father Brian Williams, who died two years ago, was left paralysed by an aneurysm at 55, according to reports.
Her eight-year-old daughter disappeared while out playing in July 2000. Sixteen days later, Mrs Payne, originally from Surrey, was told Sarah's body had been found in a Sussex field, around 15 miles from the cornfield near her grandparents' home where the little girl had been playing.
Whiting had previously served a jail sentence for abducting and sexually assaulting another eight-year-old girl.