oh lord! ok....
IN AND OUTSWING
To move the ball in an orthodox fashion away from a right-handed batsman, the rough side of the ball will be on the left side with the seam angling towards second slip.
And it is the other way round for inswing - the rough side is on the right with the seam pointing towards an imaginary leg slip.
Both deliveries also require a subtle change in seam grip too.
This generally happens when the ball is relatively new but tends to stop after the ball has lost its shine and hardness.
WHAT IS REVERSE SWING?
Once the ball becomes older and more worn, it will begin to move in the opposite direction to where it would usually swing with no great change in the bowling grip.
For example, an outswinger's grip will move towards the batsman in the air while an inswinger will move away from the bat.
All this tends to happen very late on in the delivery, making it difficult for the batsman to pick up the changes in the air.
Not every single bowler can obtain reverse swing - the ball needs to be propelled above 80mph or thereabouts to make it move in the air.
Former Pakistan international Sarfraz Nawaz was the founder of reverse swing during the late 1970s, and he passed his knowledge on to former team-mate Imran Khan.
It was Imran who schooled bowlers Wasim Akram and Waqar Younis, who brought the art to the cricket world's attention during the late 1980s and 1990s.
The dynamic duo managed to make the old ball swing a considerable distance at pace in both directions, a skill few bowlers can master.
HOW DOES IT WORK?
There have been plenty of theories about why, but here's the simplest explanation from England bowling coach Troy Cooley:
The grip is all important bowling reverse swing
"Reverse swing is all to do with the deterioration of the ball and the seam position in flight.
"As the ball becomes rougher, it will take on a different characteristic as it deteriorates.
"So if you present the ball as an outswinger, the ball has deteriorated so much on the rough side that it takes on the characteristics of the shiny side.
Which means a natural outswinger will become an inswinger and conversely, an inswinger into an outswinger."
WHEN DOES THE BALL START TO REVERSE?
Since reverse swing favours the older ball, it will usually start to move around the 40-over mark.
However, England's pace quartet, with Simon Jones and Andrew Flintoff in particular, have been able to make the ball reverse after just 15 to 20 overs.
This in particular has stumped the Australian batsman. But how have England's bowlers managed to do this so early in the innings?
Flintoff's aggressive bowling helps the ball to deteriorate
One theory could be the ball. In England, Test balls are manufactured by Dukes, while in Australia and the sub-continent the Kookaburra brand is usually used.
Like footballs, each manufacturers' cricket balls are different. Some have more pronounced seams while others deteriorate slower, all of which have an influence on how the ball will move in the air.
Another theory is how England's players are able to rough the ball up faster than other teams.
Harmison and Flintoff both bang the ball hard into the pitch while England's fielders often throw the ball back to wicket-keeper Geraint Jones on the bounce from the outfield, all of which contribute to the deterioration of the ball.
However, nothing has been scientifically proved - but batsman the world over know what to expect when the ball starts to get older.
