As the UK's top centre for investigating the effects of chemical and biological weapons, this is hardly surprising. For many years, its existence was not even widely known.

But the announcement of a police investigation into the death in 1953 of Ronald Maddison, who died after allegedly being exposed to Sarin nerve gas, changed that.

As did the news that a further 25 deaths would also be investigated, thrusting the still-functioning base in Wiltshire into the headlines again.

Hetty Nyman: Convinced of a link

One of those people believed to be at the centre of the inquiry is Fred Nyman, a welder who died in 1966, aged 45.

His wife Hetty, now 77, who still lives in Salisbury, has been battling for more than 30 years for an inquiry into the base.

Now she feels she has got exactly what she wanted.

Between 1961 and 1966 Mr Nyman, who was employed at the centre, received 19 injections which he was told were immunisations. They included doses of anthrax, smallpox, polio and bubonic plague.

The Porton Down authorities say the vaccinations could not have led to Mr Nyman's death, which a post mortem examination found was due to cancer of the stomach.

Convinced of link

But his widow is in no doubt there was a link.

"Twenty September, 1966, that was the day," she said.

"He went out, turned round, got hold of a wet milkbottle, and ran it up my leg for fun. Then he went off whistling, happy, contented, with three gorgeous sons."

Then Hetty went out to work herself, and returned later in the day expecting to find their home busy and noisy with their teenagers playing around.

Porton Down tries to find defences against nerve agents

"But that particular day I came in and there was not a sound. Two of the boys said daddy was upstairs ill in bed.

"I went upstairs and I had never in my life seen anything like it. You could have rung the bed clothes out, he was perspiring so much.

"I said whatever's wrong with you, and he said: 'I've had that bloody American bubonic plague injection.'"

'Adverse reaction'

A doctor advised Mrs Nyman to give her husband two Aspros, and see how he felt in the morning.

But the next day, when he was still ill, it was found he had suffered an adverse reaction to the injection. On further investigation, something was discovered in his stomach which at first was thought to be an ulcer.

Porton Down boss Paul Taylor

It turned out to be a cancer and Mr Nyman died in December, less than three months after the injection.

His wife says he had never been ill, and had in fact been given a thorough medical check-up and all-clear by military doctors just weeks before the vaccination.

Many of those who have been campaigning for an inquiry voluntarily took part in tests. But Mrs Nyman says her husband was made to have the injections as conditions of the job.

"If he didn't have the injections, he'd be taken off the job, he'd be downgraded. No injections, no job, that's the simple way to say it," she said. "They were guinea pigs."

Grateful at least

Whether or not the injections were the cause of her husband's death, she is grateful that calls for an investigation have been heard.

Three weeks after Frederick's death, she tried to get newspapers interested in her story. But as few people had heard of Porton Down, she was unsuccessful.

Then one day on impulse she got in a taxi and went to 10 Downing Street to try to talk to someone about what had happened.

A security officer took her to a hut and gave her a notepad on which to write a note to the then prime minister, Harold Wilson.

The PM's office did reply to Mrs Nyman, "two of the most caring lines I had ever received", with a promise that Mr Wilson would be making inquiries.