A mentally-ill man killed his grandmother in a "frenzied and vicious" attack two months after he was released from a psychiatric hospital, a court has heard.

Kordian Filmanowicz, 21, of Mitcham, stabbed and slashed 62-year-old Ilona Czuper dozens of times, removed her eyeballs and "almost obliterated" her head, as well those of the family's pet cat and dog at their family home.

The paranoid schizophrenic has admitted one count of manslaughter on the grounds of diminished responsibility at the Old Bailey.

Prosecutor James Mulholland QC told a sentencing hearing on Tuesday that Filmanowicz had a "fixation" with eyes, believing they "represented the demons of those behind them", and thought he was Jesus.

Mr Mulholland said the defendant had spent some six months in psychiatric hospitals but was released on May 8, 2017, about two months before the brutal killings in Edgehill Road on July 6 that year.

During his stay at a unit in Croydon on December 2, 2016, he threatened a staff member "in an aggressive way" with a plastic teaspoon by saying he would remove her eyes with it, Mr Mulholland said.

But senior psychiatrists released him into the community on medication after deciding he had made a "huge improvement" and his delusional thoughts were "less intrusive", the prosecutor said.

The family had moved into the area covered by the South West London and St George's Mental Health NHS Trust and visits by mental health teams "certainly slowed down" as a result, Mr Mulholland said.

However, Filmanowicz quickly deteriorated, stopped taking his medication and threatened the dog with a rock, believing it was possessed by a demon, the court heard.

The trust assessed him at home but he refused voluntary hospital admission so a full assessment was to be scheduled, the court was told.

"It will appear from notes no assessment could be arranged for the period between June 23 and Ms Czuper's death," said Mr Mulholland.

Filmanowicz's mother and sister returned home from work to find a trail of blood leading to their garden.

Ms Czuper had more than 60 slash and stab wounds to her throat as well as further injuries to the rest of her body from a "frenzied and vicious attack" while a paving slab was also used to crush her skull and the pets", Mr Mulholland said.

He added that Filmanowicz began exhibiting mental health issues during a stay in his native Poland and, after returning to the UK in 2016, started talking about demons and believing he was Jesus.

Filmanowicz, wearing a grey tracksuit, appeared emotionless in the dock.

He was remanded in custody until Thursday while Judge Anthony Leonard QC considers whether to make a hospital order.