A mentally-ill woman was able to kill her children because of "serious and cumulative failures" by authorities in east London, a coroner has ruled.
Antoine Gamor-Ogunkoya, 10, and his sister Kenniece, 3, were unlawfully killed by Vivian Gamor at their Hackney flat in 2007, ruled Selena Lynch.
Gamor, a paranoid schizophrenic, had only recently been released from hospital when she killed her children.
Ms Lynch said the risks had not been properly recognised or managed.
Gamor bludgeoned Antoine to death with a hammer and suffocated Kenniece with cling film at her flat in Pembury Close, in January 2007.
'No parental responsibility'
Had social service and mental health workers, in Hackney, better-managed the case, "it is probable that the mother would not have had unsupervised overnight contact" on 26 January, said Ms Lynch, Assistant Deputy Coroner for Inner London North.
The children's father, Gabriel "Jimi" Ogunkoya, told Poplar Coroner's Court, east London, authorities had informed him there was not much he could do to stop his partner seeing her children.
He said he had told social worker Catherine Edwards that Gamor - who had originally been sectioned under Mental Health Act after threatening a relative with a knife in 2006 - was given overnight contact with the children after just one brief supervised day visit.
Mr Ogunkoya said he had not felt comfortable with the decision because Gamor had also recently been released from hospital and had not spent time with her children for several months.
He said: "Catherine Edwards told me that there is nothing to stop her from seeing the children as I don't have parental responsibility.
"I didn't have a leg to stand on."
This prompted Mr Ogunkoya to seek legal advice about getting parental responsibility, during which time he allowed two overnight visits by Gamor that seemed to go well.
However, during her third visit she killed the children.
The court heard the couple's relationship deteriorated around 2002 and two years later Gamor started denying the two children were hers.
By January 2006, Mr Ogunkoya was in contact with social services and Gamor had been stopped from seeing the children.
But after her condition apparently improved, she was allowed unsupervised access to her children, who were in the care of Mr Ogunkoya.
An inquiry was launched after Gamor was detained indefinitely, after a hearing at the Old Bailey in August 2007, at which she admitted two counts of manslaughter.