The brother of former EastEnders actress Gemma McCluskie, found dead in a canal, pleaded guilty on Friday to her manslaughter.
Tony McCluskie, 35, claims to have "suffered loss of control" leading to her death on March 1.
Prosecutors are still waiting for a medical report to establish how she died.
McCluskie appeared at the Old Bailey by videolink from Belmarsh prison. His father, Tony senior, watched from the back of the court as he was asked to enter his pleas.
McCluskie, wearing a dark suit, pleaded not guilty to murder followed by a guilty plea to manslaughter.
Judge Gerald Gordon said this meant a trial on the issue of murder or manslaughter would go ahead on January 14 before Mr Justice Fulford.
An expert on amnesia is expected to be called by the defence.
Judge Gordon was told that Miss McCluskie's body was found in the Regent's Canal in east London in March.
A trial was due to take place last month but had to be put off because her head was discovered in September.
The judge said the trial must not be further delayed. He said: "The family must have closure."
McCluskie lived in Hackney, east London, with his 29-year-old sister.
She went missing after attending the £650 million opening of the new Royal London Hospital in Whitechapel, east London.
Her limbless body was seen floating in the water a week later.
Miss McCluskie played Kerry Skinner in the BBC soap in 2001.
The defendant joined friends who launched extensive searches across east London to find her.
Former EastEnders co-stars Natalie Cassidy and Brooke Kinsella both appealed on Twitter for help.
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