A primary school caretaker accused of injuring eight people in a letter bomb campaign had a bedroom like a "bomb factory", Oxford Crown Court has heard.
A letter bomb was allegedly sent to the DVLA offices in Swansea
When officers arrested Miles Cooper, 27, at his home in Cambridge, they found three more devices assembled and packaged, said John Price, prosecuting.
He said references to animal rights on envelopes may have been a smokescreen.
Mr Cooper denies charges relating to sending letter bombs to addresses across Britain in January and February.
Receptionist Michelle Evans opened a letter bomb, the court heard
Defence barrister Michael Wolkind QC told the jury Mr Cooper did not deny sending the devices but said he was not responsible for the injuries caused.
He sent them because "of an overbearing and over-intrusive surveillance society," Mr Wolkind said.
Mr Price told the court the alleged letter bomb campaign had caused widespread public alarm and sparked a large-scale police investigation.
He said receptionist Michelle Evans, of Orchid Cellmark, a company which processes DNA samples, was among the first on the receiving end of the letter bombs.
She had been opening the post on 18 January, as she did every morning, when she came across a "light, spongy" envelope, he said.
Miss Evans opened the envelope with a letter knife and tried to pull out the piece of paper she found inside, the jury heard, but it appeared trapped in the fold.
"She held it at arm's length and tugged at the piece of paper, whereupon the envelope exploded," said Mr Price.
"There was a very loud bang and, as a result of the shock, she dropped the envelope and let out a shriek."
Mr Price said the envelope bore the words "Dr Barry Horne, RIP" - the name of a "notorious animal rights terrorist" who died on a hunger strike.
It also included the address of the Cambridge Labour Party office and a small Animal Liberation Front (ALF) logo.
Mr Price said the bomb squad found the remnants of a small explosive device - "the first of a series of similar devices to be received in the post over the course of that day".
On the same day, LGC Forensics in Abingdon, Oxfordshire, and the Forensic Science Service in Birmingham, received similar devices in the post.
Another device was addressed to Alpha Security, sent to the company's boss at his home address in Kent.
The charges, which Mr Cooper denies, are:
Using an explosive to cause injury to Michelle Evans at Orchid Cellmark, which processes DNA samples, in Abingdon, Oxfordshire, on 18 January
Sending an explosive substance to LGC Forensics in Abingdon, and to Forensic Science Service in Birmingham
Causing injury to Michael and Rosemary Wingfield at an address in Folkestone, Kent, on 3 February
Causing injury to Maja Kurcwald at the London offices of Capita, which deals with criminal records and London's congestion charge, on 5 February
Causing injury to Richard Gorringe at Vantis, which administers speed cameras, in Wokingham, Berkshire, on 6 February
Causing injury to Karen Andrews, Jean Porter and Christopher Phillips at the Driver and Vehicle Licensing Agency in Swansea on 7 February
Making an explosive substance
Possessing an explosive substance