In October 2013 around 400 pupils arrived at their primary school in North London to find that a UFO had crashed into their playground. The object, which appeared to be some sort of spacecraft marked with what looked like an alien language, had ripped up pieces of tarmac and was now wedged firmly in the ground. The whole area was cordoned off and a local police officer guarded the scene with a grave look on his face. A man dressed in a radiation suit was apparently searching for evidence. Astonished, the pupils were led inside the building and asked to write what they thought the best explanation for what was happening.

For some of the children, well-versed in the conventions of science-fiction and fantasy, this was an opportunity for their imaginations to let rip: to bring the excitement and drama that had hitherto existed only in stories into the…