When the Soviet Union detonated the 50-megaton Tsar Bomba weapon in 1962, the world was horrified at its immense size and power - but relieved when it seemed that there was limited radioactive fallout. Now research in the Merlin database has found that a secret Whitehall committee knew toxic dust was blowing across the British Isles, and decided not to tell anyone. Special guests Alice Shadbolt and Dr Chris Hill from the University of South Wales discuss the discovery of the new document, and what it means for our understanding of the events around the decision to explode the world’s biggest bomb.

Historian Dr Jon Hogg and investigative reporter Susie Boniface introduce their ground-breaking research project at the Centre for People’s Justice at the University of Liverpool. After 70 years of fighting for the truth about their exposure to radiation at Britain’s nuclear weapons tests, veterans and families were resigned to injustice. After Susie uncovered a secret blood testing programme, hidden being national security at the Atomic Weapons Establishment, she was able to force the declassification of 28,000 top secret records. But getting to the bottom of the Nuked Blood Scandal was an impossible task, which is where the Arts and Humanities Research Council, and the university, stepped in. With funding and a team of volunteer students they are now starting to uncover the truth. Susie recalls the moment when the scandal unfolded, and they discuss how the project works with students Elliot Stephenson and Sarah-Jayne Stroud.

All the historic documents shown onscreen or in credits are Crown copyright and likewise usable under open licence, with personal data redacted.