By Nigel Pankhurst BBC News

Letter bomber Miles Cooper sent a series of explosive packages around England and Wales in January and February this year.

He cited as his motivation an "overbearing and over-intrusive surveillance society".

Miles Cooper had a "bomb factory" at his home

In the dock Miles Cooper looked a harmless, if haunted, figure.

The 27-year-old primary school caretaker from Cambridge, with his gold-rimmed spectacles, pointed features and slim frame, appeared to be vulnerable.

But for 21 days earlier this year he was responsible for a security alert across England and Wales.

In that time he sent seven letter bombs - all but two of which went off - causing significant injury to eight people.

Each time he struck, there was a flurry of activity by the emergency services and military. And - the question was - where and when would be next?

Shards of glass

Oxford Crown Court heard from an explosives expert that Cooper used two different types of bomb.

One type was designed to fire a nail at the victim. The other sprayed shards of glass.

Cooper first struck on 18 January at three locations. At Orchid Cellmark in Abingdon, which processes DNA samples, receptionist Michelle Evans, who was pregnant at the time, was injured by a device.

Letter bombs were intercepted at LGC Forensics at Culham, near Abingdon, and the Forensic Science Service in Birmingham.

The rest of the devices also caused injuries.

More victims

Michael Wingfield, who ran a security firm, and his wife Rosemary, at home in Folkestone, became victims on 3 February.

The offices of the DVLA in Swansea were Cooper's final target

Next was Polish office worker Maja Kurcwald, who worked at Capita in Victoria in central London, on 5 February. The firm's activities included dealing with criminal records and London's congestion charge.

Richard Gorringe, who worked at financial firm Vantis in Wokingham, was injured when a device went off the following day. The company was linked to the administration of speed cameras.

The Driver and Vehicle Licensing Agency was the seventh and final target on 7 February.

Employee Karen Andrews, who opened the package, and colleagues Jean Porter and Christopher Phillips were hurt.

Serious injuries

The prosecution accepted that none of the devices was capable of killing anyone, but said they were "sadistically conceived" to cause unpleasant and painful injury.

The jury listened as victims described sustaining a range of injuries including glass being embedded in hands and stomachs, and severe hearing loss from bangs produced by the blasts.

In court, Cooper's defence counsel said he did not deny making or sending the devices but that he did not intend to cause harm.

He sent them, it was said, because of an "overbearing and over-intrusive surveillance society".

When he was interviewed by police it also emerged he had written to the House of Lords in protest at proposals for ID cards.

Cooper said he was angry with authority, and called the UK "one of the most watched societies on the planet".

The court heard his feelings got stronger after his father was cleared of assault but was unable to get his DNA records removed from the national database.

'Exceptional and extreme'

Sociologist Professor Nigel Gilbert, of the University of Surrey, an expert in surveillance technology, told the BBC News website that a sense of being watched can create fear in people.

Cooper was arrested at his home in Cambridge

"This person's views are exceptional and extreme but I think in general there is well known to be a relationship between surveillance and trust," he said.

"If there's a lot of surveillance going on it leads to uncertainty. People don't know what is being watched, what is going to be done with the data that's collected - so they're uncertain and perhaps fearful.

"That fear and uncertainty can lead to loss of trust in government and society.

"Obviously in this particular case it is extreme but I think it's generally the case that the more surveillance people can see the more uncertain people are."

Devices prepared

The jury saw photographs of Cooper's bedroom and garage at the house he shared with his mother Lorraine and sister Sally.

What officers found in an early-morning raid on the home in Cherry Hinton on 19 February was "basically a bomb factory", said the prosecution.

There were three devices already prepared and addressed. Fireworks, matches and bomb-making equipment were found.

There were also the party poppers Cooper used as initiators in his bombs.

He told officers there was sulphuric acid in a cupboard and "incendiary devices".