On Monday, the court was told by prosecutor John Price that the series of attacks had caused "widespread public alarm" as police and public alike tried to work out where the next bomb would arrive.

On Tuesday, Mrs Andrews told Oxford Crown Court that, as she opened the envelope, she joked: "Do we think this is suspicious?" She told the court: "I was just joking. It was because it was a Jiffy bag and because of what had been on the news."

She described how she broke the seal on an envelope contained within the original package and saw a bright flash and heard a very loud bang.

Mrs Andrews has suffered from post-traumatic stress disorder since the incident, the court heard, a condition which worsened following the recent car bomb attacks outside West End nightclubs in London. She suffers from permanent tinnitus and has a large scar on her upper chest where she had to receive stitches.

She told the court that she has only returned to work intermittently and said: "I've been forced out of my department because some colleagues refuse to work with me. One manager even wanted me to apologise to people for what I did that day."

The court heard how the bomb had been addressed to the IT manager of an old DVLA office which no longer exists. Most of the company's large volume of mail that it receives each day is opened automatically, but items sent to an old postcode, the court heard, are opened by hand in a separate room and the backlog this creates could mean that the bomb was received as early as Monday that week.

Cooper denies eight counts of causing bodily injury by means of an explosive substance, two counts of using an explosive substance with intent to disable and making and possessing an explosive substance.