The mysteries of "reverse swing" have baffled even the most knowledgeable cricket fans for years.
Take a brand new, highly laquered cricket ball, throw it at 90 mph (145 kph) and it will usually go straight, deviating very little in the air.
Many fast bowlers can, by the way they grip the ball, make it swing in the air away from a right-handed batsman, making it difficult as he may tip the ball and be caught behind or in the slips.
As the ball gets older and is hit by the bat, smashed onto the ground or even into boards at the side of the ground, it loses its shine and takes on a battered appearance.
If the fielding team keeps one side of the ball in as pristine a condition as possible by rubbing it on their clothes or adding sweat to it, keeping it bright red, shiny and smooth, the ball will start to do interesting things when it is bowled.
The science is easily explained. One side of the ball is now slick and shiny and meets little wind resistance when it is thrown.
The other side of the ball is battered and has bits of leather protruding.
Because of the bigger surface area of one side, a bowler can make the ball deviate either inward or outward depending which side of the ball is facing out.
As the ball gets more battered, it becomes possible to swing the ball inward toward the batsman - the famous reverse swing. A batsman does not know the ball is suddenly going to swing in toward his stumps until it either crashes into his stumps or his toes.
"Encouraging" the ball to take on the qualities it needs to swing inward is where the cheating comes into it.
Soaking one side of the ball in water, picking holes in it with a bottle top or a finger nail, rubbing in grit or dirt or even applying lip gloss or hair wax have been reported as bowlers seek an unfair advantage.
Letting the ball age naturally means that it will often, when it is 60 or 70 overs old, start to reverse swing.
Umpires become suspicious that players are tampering with the ball if it starts to swing in the 40th or 50th over of an innings.
On Sunday, the ball was 53 overs old when umpire Darrell Hair demanded to see the ball and penalized Pakistan for ball tampering, sparking off the row that saw play abandoned for the day when Pakistan protested their innocence.