A primary school caretaker who carried out a nationwide letter bomb campaign will serve at least five years in prison after he was given an indeterminate jail sentence today.

Miles Cooper, whose actions injured eight people, was sentenced by Judge Julian Hall at Oxford Crown Court after he was found guilty on 11 charges relating to explosive devices.

He claimed that his targets — including forensic science laboratories and the Driver and Vehicle Licencing Agency — were responsible for turning Britain into a “surveillance society”. He admitted sending seven bombs, five of which exploded, showering victims in glass and nails.

He sent the devices to offices in London, Berkshire, Oxfordshire, Kent, Birmingham and Swansea in January and February. The victims received burns and cuts to their arms, bodies and faces. One office worker has permanent damage to her hearing.

Judge Hall told Cooper he would have given him a 10-year sentence but ruled that he was a danger to the public and handed him an indeterminate sentence.

“First and foremost you are a terrorist, let there be no mistake,” he said. “Anyone who tries through violence or threat of violence to change the political will is a terrorist and that is precisely what you did.”

Cooper was a coward who had caused lasting psychological damage to his victims and had caused massive disruption, the judge said.

“Either what you did was rational, in which case it was evil, or it was irrational which, in my mind, makes it even more frightening. You didn’t follow up your campaign of terror with any attempts at publicity trying to make your point. It makes one doubt your motives. I think you had a double motive and simply didn’t care if people were hurt.”

The judge described the bomber as an “unemotional young man with little empathy for others” who would have continued his campaign had he not been caught. “Why should I believe your experiments had ceased? Why would you ever have stopped your campaign? I have no hesitation in finding you a serious risk of harm to the public. If ever the public should be protected from someone it is you.”

He added that he was dismayed that Cooper was able to download all the information he needed to make the bombs from the internet.

Michael Wolkind QC, for the defence, said he was “lost and obsessed by his misguided campaign”.

He added: “He wasn’t planning to escalate the campaign, he was trying to devise a series of items that would cause less harm.”

Mr Wolkind said Cooper had told a psychiatrist: “An urban guerrilla is useless when discovered.”

Julian Richards, Cooper’s solicitor, said outside court that his client wished to apologise to his victims. “He has never sought to deny responsibility for sending these devices, he simply maintains that it was never his intention that the recipients should be caused serious harm. He would at this stage like to express that he is sincerely sorry that any individuals were harmed by his actions.

“These actions were motivated by, as he perceived it, the Government’s concerted and ongoing efforts to control its citizens, eroding their civil liberties and hard-won freedom.

“Of particular concern to him are the recent Government proposals in relation to ID schemes and an extended DNA database. He can’t explain why he chose to register his protest to this in such an extreme manner - all he can say is that he felt compelled to after peaceful methods that he employed were not successful.”

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