underworld boss poses such a high escape risk in the prison system that he has been placed in a special security unit, described as a 'prison within a prison'.

Bodybuilder Colin Gunn, 41, who is serving 35 years for the revenge murders of an enemy’s parents is also under 24 hour surveillance.

The crime boss spends 22 hours in the concrete cell at Belmarsh jail which was originally built in 1991 to house IRA prisoners.

A source told the Mirror: 'He’s so dangerous his lock-up is like Silence of the Lambs.'

Trained officers, who have been instructed to call him 'Mr' after he complained that he was not treated with enough respect, can enter through airlock doors monitored by video surveillance.

Unable to mix with other prisoners, he also has his own exercise yard.

Gunn, who amassed a £15million fortune from drugs, extortion and violent crime, was originally held in Long Lartin, Worcestershire.

He was transferred to the South East London jail last year after fears he plotting an escape, but it is believed he is still planning to get out. 

It is believed that as despite being locked in the high security cell, he still exerts control over the prison.

It is claimed that he intimidates staff so much so that on one occasion he sent back his dinner because it didn't have gravy and some was found for him.

A surveillance dossier complied by intelligence officers revealed that Gunn had identified a fault with the audio-visual system as an ideal time to flee.

He developed a code to use when talking to visitors through a glass screen on telephones.

Gunn is under 24 hour surveillance and monitored by video but is suspected of plotting an escape

It was also noted that  two of visitors questioned staff about security, one holds a pilot license and two more claimed to lose their passes.

Gunn was jailed in 2006 for conspiracy to murder John and Joan Stirland in 2004,

The grandparents were found shot dead at their bungalow in the Lincolnshire village of Trusthorpe on August 8, 

An inquest at Lincoln Crown Court heard that the shooting was a 'revenge' attack after Mrs Stirland's son, Michael O'Brien, shot 22-year-old Marvyn Bradshaw dead outside a Nottingham pub in August 2003.

Murdered: John and Joan Stirland were found shot dead at their seaside bungalow in 2004