The British banker accused of murdering two Indonesian women in his upscale Hong Kong apartment is a narcissistic sexual sadist who had been abused while a student at the prestigious Winchester College, a court heard on Monday.

Rurik Jutting, a 31-year-old Cambridge graduate, has pleaded not guilty to murder but guilty to manslaughter on the grounds of diminished responsibility. The prosecution rejected the lesser plea.

Opening Mr Jutting's defence, lawyer Tim Parker called on Dr Richard Latham, a consulting forensic psychiatrist with Britain's National Health Service who has worked on between 50 to 75 similar cases.

Dr Latham told the Hong Kong court that Jutting suffered from recognised disorders from cocaine and alcohol abuse on top of his other personality disorders of sexual sadism and narcissism.

Mr Jutting, who previously worked at Bank of America Corp in Hong Kong, has been accused of murdering Sumarti Ningsih, 23, and Seneng Mujiasih, 26, two years ago.

The women's bodies were found in Mr Jutting's luxury high-rise Hong Kong apartment. Ningsih's mutilated body was found in a suitcase on the balcony; Mujiasih's was found inside the apartment with wounds to her neck and buttocks, the prosecutor told the court.

Mr Jutting has pleaded not guilty to murder on grounds of "diminished responsibility", but guilty to the lesser charge of manslaughter.