“We want to speak to anyone who knows where Anslow might be.”

Mr Evans added: “There’s obviously a possibility that he’s travelled abroad or may be planning to do so. If this is the case, there will be people who know about it and we want to speak to them.

“The offer of a £10,000 reward is a good incentive for people to pick up the phone and all calls will be treated in the strictest confidence.”

Anslow was one of five men charged with the murder of 27-year-old businessman Richard Deakin, who was shot dead while alone in his home in Chasetown, Staffordshire, in July 2010.

He was being taken to Stafford Crown Court on Monday when the prison van he was in was ambushed.

Three masked men, two armed with sledgehammers, burst out of a Volkswagen Scirocco car and attacked the driver before Anslow was freed.

It is known that the offenders used a silver Volkswagen Scirocco - registration BT59 NXC - before switching to a silver Mercedes, which may have been a C-Class model, with the partial registration KR11.

Mr Evans continued: “We need to talk to anybody who saw these vehicles on Monday or who has seen the Mercedes since.”

Members of the public are advised not to approach Anslow, who is considered to be very dangerous, and anyone who sees him should dial 999 immediately.

Anyone with information should ring the inquiry incident room on 01785 235051 or the independent charity Crimestoppers anonymously on 0800 555 111.