In a field in Oxfordshire is a colossal steel and concrete bunker that scientists call the monolith. At the centre of this 6,000-tonne shell is a lump of metal the size of a packet of biscuits that produces 20,000 million million neutrons per second.

The monolith is the heart of one of the most extraordinary machines ever built. The beams of neutrons it produces allow scientists to penetrate deep inside objects to understand the most intimate molecular details of their internal structure.

"Essentially Isis is a giant microscope. It enables us to see where atoms are and what they are doing. If you know where the atoms are and how they are joined together, we can essentially understand the material."