How do you dismantle a nuclear bomb? And how do you verify another country is genuinely disarming without compromising sensitive national security material?
BBC security correspondent Gordon Corera was given exclusive access to a unique exercise run by the UK and Norway to find out.
The nuclear weapon is carefully lifted out of a large container and moved onto the floor.
Two engineers use an electric screwdriver to open up a side compartment and remove the "physics package" containing the sensitive parts of the bomb.
A scientist with a radiation detector beckons me forward as he points his machine towards the box.
It begins to emit an accelerating beeping noise. "The measurement is approximately a hundred times normal background radiation," he tells me.
"But it is not dangerous, I promise," he adds with a smile.
The lack of danger is because the bomb is not real.
|Liveleak on Facebook|