When Sussex were playing Hampshire in 1981 the ball was not deviating at all.

Sphericity, or deviation from spherical form, refers to how much the ball deviates from a true spherical form (out of roundness).

This changes the axis of spin to make it more like an off break, which makes the ball deviate to the right when it bounces on the pitch.

Unusually for a bowler of his pace, he could make the ball deviate from straight, either through seam movement or cutting his fingers over it before release, but most of his wickets were taken through sheer speed.

Occasionally, however, the ball can deviate far enough to hit the edge of the cricket bat instead of the middle, producing a catch for nearby fielders.

Otherwise, Hutton and Compton progressed steadily before the light deteriorated, although Johnson and Toshack were able to make the ball deviate regularly.

The Katchet is a fielding aid which mirrors random deflections encountered when the ball deviates after hitting the bat or wicket.

There is no way with his hand-to-eye co-ordination that he'd miss that unless the ball deviated.

The ball deviated in the air but what cost the Pole was his starting position, the keeper too rooted to the line, allowing Walker's drive to fly past him.

A bowler who achieves swing when bowling yorkers can be even more dangerous, as the ball will deviate sideways as it travels towards the batsman, making it even harder to hit.