From the safety of a computer screen in the control room, I can see a robot scoop up a chunk of asbestos from the reactor floor. I am at Sellafield, the nuclear complex on the coast of Cumbria in north-west England, watching remotely controlled machinery crawl through the defunct Windscale Advanced Gas-Cooled Reactor, gradually stripping out the last of its guts. The mammoth task of dismantling the reactor started in the early 1990s but is only now finally nearing completion.