Veterans and civilians involved in nuclear tests in the 1950s and 1960s have started legal proceedings against the British government after claiming exposure led to chronic illness.
An unknown number of complainants plan to take action against the Ministry of Defence.
Thousands took part in the tests, which were held in Australia, Christmas Island and other islands in the South Pacific.
The tests included the detonation of a large number of nuclear devices by both Britain and America.
Troops from the UK, the Commonwealth and the US were involved and many civilians also allegedly witnessed the nuclear programme.
The veterans claim they were not given suitable protective clothing and were exposed to atomic radiation, which has been denied by the Ministry of Defence.
Some said the negative side-effects were evident at the time while other veterans died from radiogenic cancer, allegedly linked to the tests.
Solicitor Mervyn Fudge said he thought the complainants would be successful.
He said: "Recently-published research shows that the stance taken by the Ministry of Defence is incorrect and that the veterans have sustained injuries which should allow them to claim compensation from the British Government.
"From the information which is available to both ourselves and Alexander Harris, we are at this time satisfied that such an action is sustainable and would be successful."
PA