A PRISONER who sent Bullingdon Prison into a “deep freeze” with a bomb threat was jailed for six years yesterday.

Mark Walker also sent threats to Home Secretary Theresa May after becoming frustrated with the probation service, Oxford Crown Court heard.

The 39-year-old wrote to her from his cell at the prison near Bicester and said: “Watch your back. You are a dead woman.”

The court also heard Thames Valley Police said Walker had cost them nearly £17,500.

When Walker was in jail for child sex crimes prison officers found a document entitled ‘Plan of Action’ in a cell search last June.

The court heard the plan involved going to Miss May’s Berkshire home and “causing problems”.

He had been jailed in 2003 for 10 years for child sex crimes including raping a girl under 16 and last February he was jailed for six months for distributing indecent images of children.

When Walker was released in August he made a telephone call claiming there was a bomb at his hostel in Windsor.

He was taken back to prison and from Bullingdon he rang Crimestoppers and told them there was a parcel bomb at Miss May’s home.

In April, he claimed there was a mail bomb at the prison and caused significant disruption as judicial visits and prisoner transfers were cancelled, the court heard.

Iain Wicks, prosecuting, said: “The ordinary running of the prison was utterly halted and put into a deep freeze by this single action.”

Recorder John Hardy, sentencing, said: “Your actions caused the diversion of scarce public resources.”

Walker admitted two charges of communicating false information with intent, using a public communication network to send a menacing message, and one of sending a letter conveying a threatening message.