London Marathon 2014: Professor Greg Whyte's marathon top tips

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Need the toilet? Essential marathon tips

Fitness expert Professor Greg Whyte offers up some essential advice on running a successful marathon.

He offers some light-hearted advice on warming up, going to the toilet and how much to eat and drink along the way.

Whyte competed in modern pentathlon twice at the Olympic Games and is the man who pushed David Walliams,Eddie Izzard and Davina McCall to their physical limits for Sport Relief.

Watch comprehensive coverage of the 2015 across BBC Sport.

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