Clive King's Stig of the Dump is a much-loved modern classic.
 
It is the story of Barney and his best friend, cave-man Stig.
 
Barney is a solitary little boy, given to wandering off by himself.
 
One day he is lying on the edge of a disused chalk-pit when it gives way and he lands in a sort of cave.
 
Here he meets 'somebody with a lot of shaggy hair and two bright black eyes' wearing a rabbit skin and speaking in grunts.
 
He names him Stig. Of course nobody believes Barney when he tells his family all about Stig, but for Barney cave-man Stig is totally real.
 
They become great friends, learning each others ways and embarking on a series of unforgettable adventures.