There was stark criticism particularly for his father Alphonse Rudakubana, who Sir Adrian said had deliberately withheld information about his son amassing a stash of deadly weapons including the biological toxin ricin.
Sir Adrian said if the parents had reported their true level of knowledge to the authorities before the attack, the killer would “undoubtedly have been taken into care or held in custody”.
He did accept that Rudakubana had made his mother and father’s lives “a nightmare” and parenting him had been “challenging”.
Giving evidence during the inquiry last year, his father Alphonse Rudakubana tearfully apologised and said he regretted not contacting the police about his son following a range of troubling incidents in the months and weeks before the attack.
“The love I had for him overrode [my] good judgement,” he said.
Sir Adrian said the killer’s parents had failed to act out of a “misguided and irresponsible” desire to avoid him being taken into care.
Speaking after the report’s conclusions were made public, Sir Adrian said: “Numerous systems that should have provided oversight, assessment and protection were ineffective or inadequately used. Some failed outright.
“The consequences were catastrophic.”
The Phase One report came after months of evidence from police officers, medical professionals, social workers and teachers – as well as witnesses, survivors and parents of the children both killed and wounded.
The 67 recommendations of the report call for a joined up approach with agencies able to share information more effectively.