Inspector Glenn Wickes: "He is dangerous and under no circumstances should he be approached"

A post-mortem examination revealed that Margaret Thomson, 38, died of severe head injuries. Her body was found at her Derby home on Thursday.

Ms Thomson started a relationship with Mark Leicester after she visited him in prison out of charity. He was serving a life sentence for the murder of his girlfriend.

He had been allowed out of Sudbury Prison, Ashbourne, Derbyshire, for the day to work at a centre for the mentally and physically handicapped.

Nationwide manhunt

Detectives believe he was in Leicester city centre on Friday morning. Inspector Glenn Wickes warned the public not to approach the suspect, describing him as "extremely dangerous".

He added: "This is now a nationwide manhunt and every force in Britain is on alert as are all ports and airports.

"We know he has extensive knowledge of the bus and railway network and passengers should be especially vigilant."

Police believe Leicester may now be headed for Scotland. A former partner of Ms Thomson, who lives on the Isle of Bute in Scotland, is still under police protection, after receiving death threats over the phone.

Police request information

Forensic experts have recovered a number of items from the scene, which have now been sent for further analysis. No other weapons are being sought.

Specially trained officers are hoping to interview Ms Thomson's two daughters, aged six and 17, later on Saturday. It is understood that both are so distressed that it may not be possible.

Leicester is described as clean-shaven with a fresh complexion, 5ft 8ins tall, with green eyes and brown hair.

Anyone with information should call Derby police on 01332 290100.