He confronts the head keeper, who initially denies this but finally admits that there is such a beast - the Blue Gorilla. It takes a great deal of further persuasion to be allowed to see the creature, and permission is only granted if the man promises not to touch it.
He is led through a steel door, along a tunnel deep below Corstorphine Hill. At the end of a concrete-lined corridor, behind thick steel bars, the Blue Gorilla sits placidly munching on a banana. Overcome by the beauty of the gorilla's luxuriant blue fur, the man reaches through the bars to stroke it.
Immediately the Blue Gorilla leaps to its feet, roaring. Turning tail, the man races back along the corridor, but the gorilla has wrenched the bars from its cage and is gaining on him. The man slams shut and bolts the steel door. But the Blue Gorilla passes through it, hardly slowing as it leaves a Blue Gorilla-shaped hole in six inches of solid metal.
The man runs out of the zoo onto Corstorphine Road. He boards a bus (an airport special that is fortuitously passing) and collapses in the back seat.
After a time he looks over his shoulder. Half a mile back, kicking up a stoor and advancing rapidly, is the Blue Gorilla. Panic stricken, the man alights at the airport and bluffs his way on to a flight for Cape Town.
All goes well until they overfly the Med. Thousands of feet below his window, the man spots the Blue Gorilla, matching the plane's speed with a powerful front crawl.
He bales out over the Sahara, reasoning that his nemesis will not be able to tolerate the intense, dry heat. He is wrong. As he crawls, thirsty and exhausted, across the desert, the gorilla approaches at the centre of its own personal sandstorm.
Finally beaten, the man falls flat and rolls on his back, only to see an enormous shape loom over him. The Blue Gorilla raises a might arm and brings its hand down on his shoulder.
"Tig!" says the Blue Gorilla, and lopes off back to Edinburgh.
Now what disturbs me about this story is that when I told it to my S2 science class, on their last day of last session, I held their attention as I never had before.
* Gregor Steele recommends plenty of arm swinging and gorilla noises when telling this story.