A former porter at a children's hospital who has admitted dozens of sex abuse offences against children kept a diary of the threats and bribes he used to coerce one of his victims, a court has heard.
Paul Farrell, 55, worked at Great Ormond Street Hospital (GOSH) in central London between 1994 and 2020, but did not target children there.
He has admitted 69 offences against eight victims over 35 years, but prosecutors say the counts were "multi-incident" and represent at least 560 offences.
And the real total, they say, is "likely to be in the thousands".
He accessed victims by befriending their parents and acting as a babysitter so he could carry out his abuse at addresses across the city.
In one case, Farrell, from Camden, north London, sexually abused three brothers.
A diary in which "he noted down, day by day, his strategy to keep them under his control" was found on one of the defendant's phones, prosecutor Paul Douglass told Wood Green Crown Court.
In numerous entries, he would remind himself to buy presents for members of the family, or to offer himself as a babysitter.
Farrell employed "malicious threats, bribes and promises" during a three to four year period to manipulate one of the brothers, who was aged 12 when the abuse started, Mr Douglass said.
One diary entry read to the court said to "give (the victim) £10 for letting me stay in his room", while another said: "If I ever got caught your parents will be very angry and I will just have to disappear."
The abuse, Mr Douglass said, would start when the victim was asleep, adding: "He frequently expressed his distress to the defendant at what the defendant was doing to him.
"He mentioned trying to push him away when he was being abused, and he would often hit him out of anger at what he was doing."
Mr Douglass said the victim's two younger brothers were abused by Farrell in the bedroom they shared, with the abuse happening while they were both in the room.
In a victim impact statement read by Mr Douglass, the boy said he cried himself to sleep during the abuse and described feeling suicidal following his ordeal.
He said: "I felt I had no right to do anything and I was restrained, so I had no control over my own body. I felt useless. I felt like I had no input, nothing."
The offences, carried out between 1985 and 2020, include attempted rape, sexual assault of a child under 13 and making indecent photographs of children.
The total number of offences Farrell will be sentenced for is 76, including seven offences related to possession of indecent images of children.
A spokeswoman for GOSH earlier said: "We would like to reiterate what has been said in court, that Paul Farrell did not target children at GOSH."
Sentencing is expected on Monday.