A robber accused of murdering a City banker told police he agreed to burgle the man's house but not take part in a killing, the Old Bailey has heard.
Mr Monckton was repeatedly stabbed at his home
The prosecution said that in a statement to police Elliot White also said he was restraining John Monckton, 49, when "another person" stabbed him.
Mr Monckton was attacked at his west London home last November.
Mr White and Damien Hanson, both 24, deny murder and the attempted murder of Mr Monkton's wife Homeyra.
Richard Horwell, prosecuting, said the defendant told police he had been in financial difficulties and prepared to commit a burglary.
Mr White is alleged to have said he did not know there would be people in the house, but when the door of the Monckton's Chelsea home was answered he struggled with Mr Monckton.
The defendant told police that when the man he was with started hitting Mr Monckton in the ribs he "did not realise it was with anything more than a fist", Mr Horwell said,
The statement went on: "Within a few seconds I saw there was a problem with Mr Monckton. He began to fall down. I knew it was not just as simple as just blows.
"I managed to pull him away. I was then attacked by the same person who attacked him while Mr Monckton was on the floor.
When questioned Mr White is alleged to have told police he asked the other man what he was doing as he "was under the impression I was doing a burglary".
'Obsession with the rich'
Earlier on the fourth day of the trial the court heard Mr Monckton died from knife wounds to the heart and lung.
Prosecutor Richard Horwell said the injuries to the victim's hands showed he had tried to fend off repeated knife attacks.
The prosecution claims the couple were targeted because they were wealthy - the trial has heard Mr Hanson in particular had an "obsession with the rich".
Mr Monckton's wife Homeyra, 46, was also stabbed twice in the back. The trial heard on Wednesday she had been paralysed after the attack and still uses a walking stick.
Mr White, from Shepherd's Bush, west London, and Mr Hanson, of no fixed address, deny murder, attempted murder and wounding with intent.
Mr Hanson also denies a charge of robbery, to which Mr White pleaded guilty. The trial continues.