The prolific armed robber dubbed the Skull Cracker has been jailed for life with a minimum term of 10 years today for offences including armed robbery carried out while on the run from an open prison.

Michael Wheatley, 55, was already serving 13 life sentences at Category D Standford Hill prison on the Isle of Sheppey, Kent, for a string of violent robberies when he was granted day release and failed to return on May 3.

Before being recaptured he carried out an armed raid on the Chelsea Building Society in Sunbury-on-Thames, Surrey, on May 7, pointing a handgun at staff and making off with £18,350.

Wheatley, who was recaptured in Tower Hamlets, east London, after the raid, was sentenced at Guildford Crown Court today after pleading guilty to robbery, possession of a firearm or imitation firearm while committing an offence, and being unlawfully at large.

The court heard that he previously robbed the same building society branch 13 years ago and staff had been told to be on their guard following his disappearance.

Appearing via video-link from HMP Belmarsh in south east London, he showed no emotion and sat with his arms folded as Judge Christopher Critchlow passed sentence.

Judge Critchlow said it was a ''special case'' because of Wheatley's prolific record of violent armed robberies and committing offences after being released from prison sentences.

Passing sentence, the judge told him: ''You went to the same branch which you robbed in about 2001.

''You therefore deliberately targeted this branch and planned this raid.

''You knew exactly what you were doing, having committed such crimes so many times.''

He added: ''It is clear the public must be protected from you for a long time.''

The court heard that Wheatley has 23 previous convictions for robbery, two for attempted robbery and 18 for related firearms offences.

He was given his nickname after pistol-whipping innocent bystanders during previous robberies, including a 73-year-old woman. The court heard that Wheatley has spent a total of 46 years in institutions, starting at the age of six, and has been in prison on and off for most of his adult life.

On May 6 the manager of the building society had warned staff to be on their guard, having seen the media coverage of Wheatley's disappearance.

He entered early the next morning, posing as a man who had spent 20 years in Ireland and wanted to open a new account.

After twice coming in and chatting to deputy manager Christopher Gurdev, he was about to leave when he said ''one more thing'', prosecutor Dale Sullivan told the court - ''At which point the defendant pulled out a handgun from within his jacket and pointed it at Mr Gurdev's head.''

The court was played CCTV from the robbery, which showed Wheatley forcing Mr Gurdev at gunpoint to unlock a door, take him into the back of the branch and hand him cash from a safe while shouting ''Give me the money''.

He also pointed the weapon at a female cashier.

Mr Sullivan said: ''The importance of the location of the robbery was that the branch was robbed by the defendant some 13 years ago.

''The manager had briefed her staff the night before about Wheatley, telling them to be aware of him because of the media coverage and his failure to return to Standford Hill.''

All but £850 of the money was recovered when Wheatley was arrested later the same day, Mr Sullivan said, but the gun, real or imitation, was never found.

Wheatley was sentenced on the basis that it was an imitation firearm.

Lionel Blackman, defending, said Wheatley went on the run after being refused parole after almost eight years in prison and then again last October.

He told the court Wheatley had been having therapy in prison in between parole attempts and had not applied while getting help.

But the therapy to deal with abuse he suffered as a child was stopped because of funding cuts last July, the court heard.

After his second failed parole attempt he was downgraded and moved to the Category D open prison.

Mr Blackman told the court: ''This is a case where a man has spent 46 of his 55 years in one institution or another.''

He continued: ''He was very much left to his own devices in the open prison.

''Not seeing on the horizon another opportunity to determine his release and disappointed not to achieve a release at seven and a half years or in October, he made the decision not to return to prison at all.

''The plan was to start a new life in Ireland. Regrettably he committed a robbery to fund that new life.''

Detective Chief Inspector Chris Raymer, of Surrey Police, said: ''Wheatley is a dangerous individual and I welcome the lengthy sentence imposed at today's hearing which reflects the seriousness of his crimes.

''This was clearly an extremely distressing incident for the members of staff in the building society who were threatened by Wheatley and I hope the sentence helps them to move forward.

''Officers were at the scene within minutes of the emergency call and we worked closely with Metropolitan and Kent Police colleagues, resulting in Wheatley being arrested within hours of the offence.''