BBC World Service
15 kiloton explosion, "Mosaic 1", detonated on Trimouille Island
Hundreds of veterans who witnessed nuclear tests in the 1950s have joined one of the largest compensation claims against the Ministry of Defence.
It goes back to the height of the Cold War in the 1950s, when thousands of British and New Zealand servicemen were sent to the South Pacific to witness the tests.
Some of these veterans say that the radiation they were exposed to during these tests has resulted in serious illness, including cancer.
Seven hundred of them are now seeking compensation. The deadline to join the mass action is Monday 3 March 2008.
During the last year, Rosenblatt Solicitors - the lawyers representing the 700 - have been gathering testimonies from the veterans.
New details have emerged about two of the tests involving a British Royal Navy warship, HMS Diana.
The ship was ordered to steam through the fallout from two atomic explosions, partly to test the effects of radiation on equipment.
Bob Malcolmson was an 18-year-old radio operator on HMS Diana in the 1950s.
He remembers the explosions well - especially the second one. This one was 98 kilotons - about six times larger than the Hiroshima atomic bomb.
He said: "The explosion was tremendous. They actually heard it in Australia 200 miles away from the islands. We turned our backs, covered our eyes with our hands. I had my eyes open and I could see the bones in my hands, even with my back to this thing."
According to the testimony of the recently deceased Captain John Gower, large areas of the deck became radioactive and had to be roped off.
Mr Malcolmson said that some men showed signs of radiation sickness while on board.
Bob Malcolmson, aged 18, on board HMS Diana at Monte Bello Islands
"Several chaps lost teeth, and others lost their hair. So a lot of wives and sweethearts waited in Devonport to welcome back bald fiances and bald boyfriends with a few teeth missing."
Twenty years later, in 1974, Mr Malcolmson was diagnosed with polycythemia - a rare form of blood cancer. He says his doctors have linked this to radiation exposure.
Many of the men on the ship, including Captain Gower - believe the British government was deliberately testing the effects of radiation on the men as well as the ship.
Rosenblatt Solicitors say they have evidence to prove this.
Ships company HMS Diana 1956 heading to the Monte Bello islands
They have found a document, released under the 50-year Official Secrets Act from 1953, addressed to the Chiefs of Staff Committee.
It reads: "The Army must discover the detailed effects of various types of explosion on equipment, stores and men, with and without various types of protection."
But Lorna Arnold, the official historian of the British nuclear tests, interprets this document differently, claiming the British government had no intention of carrying out tests on men.
Ms Arnold says this sentence referred to tests carried out on models. These were placed in various positions at the test site, with instruments put on them to measure the amount of radiation and blast they received.
Whether or not the men were being used as human guinea-pigs, the veterans' lawyers argue that the Ministry of Defence (MoD) should be held liable because of the high rate and specific types of illness experienced by the veterans afterwards.
'Months to live'
However, the MoD denies that radiation from nuclear tests has resulted in life-long illness.
In a statement it told BBC News: "When compensation claims are received they are considered on the basis of whether or not the Ministry of Defence has a legal liability to pay compensation. Where there is a proven legal liability compensation is paid."
Some of the veterans involved in this claim have only a few months to live. The lawyers say that 50 die every year.
But there is a chance that none of these arguments will ever come to court, as the MoD has indicated that it will use a defence of limitation.
Under this, any claim for compensation must be brought within three years of the injury.
The British courts will decide in 2009 whether a case can be brought, although for some veterans this will be too late.