Jurors were warned to pay little heed to alleged killer Robert Knapp's past as businessman Nicholas Van Hoogstraten's "dissuader".

Knapp is accused of murdering landlord Mohammed Raja with friend David Croke on the orders of Hoogstraten.

The term "dissuader" was put to the Old Bailey jury by Hoogstraten's former architect Anthony Browne.

He said 54-year-old Knapp, from County Limerick, had been called upon by the tycoon to deal with awkward tenants on at least two occasions.

However, closing Knapp's defence, Elizabeth Marsh told the Old Bailey: "This was a term used by Anthony Browne.

"He has no idea what Knapp said or did that prevented further aggravation from these two people."

Ms Marsh recalled Mr Browne had said that during an argument with Hoogstraten, Knapp ushered him out of the millionaire's office.

She said: "The man that calmed Anthony Browne down is apparently the man the Crown say Hoogstraten would have employed to murder Mr Raja."

Ms Marsh mentioned payments from Hoogstraten to Knapp in the months after the murder, claimed to be for carrying out the contract hit.

She warned: "People do not commit murder on credit."

Closing the defence of Croke, 60, from Bolney Road, Moulsecoomb, Brighton, Malcolm Swift QC referred to a blood smear on the Raja family's front door.

DNA experts said there was a billion-to-one chance it came from someone other than Croke.

In 1999 Croke delivered packages around London and the jury heard he might have visited the Rajas' home at Mulgrave Road, Sutton.

Mr Swift said: "It's a classic case of statistics triumphing over common sense and, in any event, a classic case of a total irrelevance if the DNA came there incidentally."

Croke and Knapp deny murder. Hoogstraten, 57, of High Cross, Framfield, near Uckfield, denies murder and conspiring with Croke, Knapp and others to murder the businessman.

Mr Raja was shot and stabbed to death at his home in July 1999.

The trial continues.