A porter who worked for decades at Great Ormond Street Hospital and pretended to be a "loving family man" has admitted 69 sexual offence charges against children.
Paul Farrell, 55, pleaded guilty to sexually abusing eight children between 1985 and 2020 - amounting to at least 500 instances of abuse.
He appeared at Wood Green Crown Court in London on Friday, where other charges were left on file.
Farrell pleaded guilty to charges including indecency with a child, causing a child under 16 to engage in sexual activity, and indecent assault.
The youngest victim was believed to be five years old in the 1980s.
Farrell, from Camden, had babysat some of the children, but the Crown Prosecution Service said the charges did not relate to any patients at the hospital at the time.
He was arrested in January 2020 after victims came forward and contacted police.
A safe at his home contained indecent photos and DVDs of children, while indecent images and extreme pornography were found on his phone.
Farrell pleaded guilty to five counts of possessing indecent images and extreme pornographic material of children at a previous hearing.
Jane Ndeti, from the CPS, said the paedophile had "carried out an appalling campaign of sexual abuse against eight young children over a period of 35 years".
"He was a prolific sex attacker who presented himself as a loving family man with a stable job in London's biggest children's hospital for nearly three decades," she said.
Farrell will be sentenced on 28 May.