From this page:

THE TRUTH ABOUT WILSON:

William Wilson was born at Stayling village in 1795.

At the age of 14 he ran away, and determined to improve his physique beyond normal, lived wild on Ambleside Moor. There he met a hermit who passed on to him the secret of long life.

First recorded sighting of Wilson was at the British Summer Championships held at Stamford Bridge, London in 1938.

At these Championships, Wilson leaped over the barrier onto the track, just before the start of the mile race; Wilson won the race running the mile in just three minutes.

Up to the start of the war in 1939, Wilson's athletic feats at home and abroad astounded the world.

During the war he served in the Royal Air Force as a Spitfire pilot. After winning 25 air victories he was shot down in the Battle of Britain.

After the war he devoted his skill and knowledge to helping wounded and disabled men back to normal at an Army Convalescent Hospital.

Wilson next took on the task of finding and training men to represent Britain in the 1948 Olympic Games.

He next penetrated into the African Congo, alone, and discovered an ancient Greek civilization�an African Athens. He competed against the picked Greek athletes of this secret city.

Following this, he then pitted his astounding athletic skill against Chaka�s black athletes.

Wilson saved Africa from warfare to which the Zulu leader was bringing the country.

As a supreme test of mental and physical powers, Wilson set out to conquer Mount Everest.

And that site has some chapters from Wilson stories. Mind it doesn't answer the question what happened to him. I'd imagine he's still around and will turn up again some day.