We cut our way through a tangle of vines, each one thicker than a man's arm. Heat prickled our skin. The air was humid, tropical, and thick with floral perfume: something like frangipani, with a less-pleasant undertone of... what was that? Sulphur?

When at last we pushed aside the final curtain of vines, we could barely believe the evidence of our eyes. A volcano, forcing its way up out of the ocean, and, around it, a flock of pterodactyls carrying mail bags.

We had discovered it at last: the lost island of the Prehistoric Post Offie.