Ultimate fighter Conor McGregor
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Conor McGregor: Ireland's ultimate fighter

16 July 2014 Last updated at 10:06 BST

You may never have heard of it, but mixed martial arts is said to be the fastest growing sport in the world.

This weekend some of its best-known fighters, including rising star Conor McGregor, will compete at a major event in Dublin.

The Ultimate Fighting Championship regularly attracts sell-out crowds but some doctors have raised serious concerns.

Chris Buckler reports.