"David Beckham Goes Horseback Riding" joke

David Beckham decides to try horseback riding, even though he hasn't had any
lessons or prior experience. He mounts the horse unassisted and the horse
immediately springs into motion. It gallops along at a steady rhythmic pace as
Posh stands back in admiration, but then he begins to slip from the saddle.
In terror he grabs the horse's mane, but cannot seem to get a firm grip. He
tries to throw his arms around the horse's neck, but he slides down the side of
the horse anyway. The horse gallops along, seemingly impervious to its slipping
rider.
Finally, he gives up his frail grasp and he attempts to leap away from the horse
and throw himself to safety. Unfortunately, his foot has become entangled in the
stirrup, now he is now at the mercy of the horses pounding hooves as his head is
struck against the ground over and over.
Posh stands there frantic, unable to do anything to help as his head is battered
against the ground. He is mere moments away from unconsciousness when to his
great fortune The Sainsbury's security guard sees him, leans over, and unplugs
the horse.