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The Grand National at Aintree provides a unique test for horse and jockey.

The race comprises two full circuits of a unique 2¼ mile course, and has 30 fences, with The Chair being the most famous.

Jockey Andrew Thornton, who rides in the 2016 race and has almost 1,000 career wins, joins Luke Harvey as they explain what makes the fence the most formidable in the race.

This clip is from 5 live Sport on Thursday 7 April 2016.