‘Child,’ said the Spirit of the Rainbow, though he was no older than she. ‘I remember this forest many hundreds of years ago. It was a wild, carefree place. Can you guess how many chocolate wrappers and other bits of litter there were mucking it up?’

‘Six?’ said Polly.

‘None,’ came the lad’s astonishing answer. ‘None at all. You see, child, the world was full of wonder back then. There were fauns and centaurs – yes, actual real centaurs. One of them was called Tony. And there were pixies and elves and transparent sprites with almond-shaped eyes, bathing in the streams. It was excellent.’

‘Was there unicorns too?’ asked Polly, who had always wanted more than anything to find a unicorn and ride it to the moon.

‘No, there never were any unicorns,’ said the lad. ‘That was just a myth that started when an ice cream cone accidentally got stuck to a pony’s head.’