Legendary Test match umpire David Shepherd gives his unique insights into the secret world of life in the middle in a BBC Sport Online exclusive.

'Shep' hit the headlines this summer in the second Test between England and Pakistan at Old Trafford, where controversial no-balls were missed.

He admits mistakes were made, but he is still one of the most colourful and charismatic figures in the world of cricket.

In the words of England and Wales Cricket Board chief executive Tim Lamb, 'Shep' "remains one of the finest umpires both in domestic and international cricket".

This is his definitive guide to umpiring.

All the calls and signals are displayed with explanatory text outlining why and when umpires would indicate their decisions.

Simply click on the calls displayed on the left-hand side to see what they all mean.