A paedophile doctor was able to gain the trust of his victims and their families by appearing to be the "best doctor in the world', an investigation has found.
Staff were also duped by the conduct of Dr Myles Bradbury, who was able to manipulate both them and his hospital's policies to commit sexual offences against young boys.
Bradbury, of Herringswell in Suffolk, was jailed for 22 years in December for sexual assault, voyeurism and possessing more than 16,000 indecent images.
He admitted abusing 18 boys in his care at Addenbrooke's Hospital, Cambridge, between 2009 and 2013.
Following appeal, his sentence was reduced to 16 years in custody with an additional six years on licence.
A new report for Cambridge University Hospitals NHS Foundation Trust by consultancy firm Verita found that Bradbury was able to abuse boys for years without raising serious suspicion.
Investigators found Bradbury "groomed" patients by taking an interest in their wider social lives, chatting about football, and by making parents feel special.
He repeatedly breached chaperone policies by abusing boys behind curtains even if their parents were in the room, and regularly seeing patients who were young enough to need a chaperone.
He also took advantage of flexibility in the trust's appointment booking system to meet families outside usual times.
When staff did question some of Bradbury's actions, they were always given a "plausible" explanation, the report said.
Investigators concluded that while clues had been missed, staff could not be blamed for failing to raise the alarm owing to Bradbury's acceptable explanations of his behaviour.
When one doctor did ask why he was seeing a young boy alone, Bradbury explained that the boy was being bullied and his mother had agreed to a one-to-one appointment.
Staff also noticed Bradbury was reluctant to have medical students with him when he saw patients, but they accepted his reasons.
One doctor told investigators how Bradbury had a wall covered with letters from children.
"You know - best doctor in the world. So I remember thinking 'My goodness, I've got none of those on my wall. What is this guy doing that is so fantastic for these families? By implication what is it that I'm not doing?"
The report found Bradbury was able to manipulate the policies on chaperones by befriending patients and their families and relying on the fact it was a busy department.
He also gave out his mobile number to patients and families and booked appointments directly with them, often outside usual clinic times.
One consultant told investigators that families felt Bradbury had built a rapport with them.
"All of them said 'we really liked him'. We thought he was a wonderful doctor. We trusted him implicitly."
The mother of one boy said: "He would stop and talk to people, make a big fuss of them and then go onto the next person. It was almost like you felt, 'Oh, he's going to notice me'. He was just very clever..."
The report said Bradbury went on holiday with the family of a former patient but had then agreed not to see the boy in clinic.
Another doctor noticed Bradbury seemed to be "awfully focused" on the impact of children's conditions on the development of puberty.
The trust did not have any one person monitoring chaperone policies, the report said, with investigators recommending improvements in this area.
Bradbury, who used a "spy pen" to secretly capture pictures of his partially-clothed victims, was only arrested when the grandmother of an 11-year-old boy who was asked to strip raised the alarm.
David Wherrett, acting chief executive of Cambridge University Hospitals Foundation Trust, said: "I want to say sorry again to our patients and families who placed their trust in Myles Bradbury during their treatment here, and instead became victims of his cold and calculating abuse.
"I want to reassure the families involved, and indeed all our patients, that we agree with the recommendations made in today's report and are already starting to take the necessary action."
The report's author Lucy Scott-Moncrieff said Bradbury told her he was "desperately sorry" for what he had done when she visited him in prison along with her co-author.
She told BBC Radio 4's World At One: "We went to see him when we had spoken to all the other witnesses. We really wanted to get his comments on what our tentative thoughts were and also get his views on what could be done to reduce risk in future.
"He only agreed to see us because he wanted to help us with this. He told us, and I see no reason not to believe him, that he was desperately sorry about what he had done and he realised now the extent of the harm he had done.
"So this was a sort of act of reparation."
She said his former colleagues at Addenbrooke's felt "totally betrayed by him".