Conor McGregor's trainer tells the amazing story of his long road to success in the world's fastest-growing sport.

Growing up in Dublin, John Kavanagh was a skinny lad who was frequently bullied. As a young man, after suffering a bad beating when he intervened to help a man who was being attacked, he decided he had to learn to defend himself. Before long, he was training fighters in a tiny shed, and promoting the earliest mixed-martial arts events in Ireland. And then, a cocky kid called Conor McGregor walked into his gym...

In Win or Learn, John Kavanagh tells his own remarkable life story - which is at the heart of the story of the extraordinary explosion of MMA in Ireland and globally. Employing the motto 'win or learn', Kavanagh has become a guru to young men and women seeking to master the arts of combat. And as the trainer of the world's most charismatic champion, his gym has become a magnet for talented fighters from all over the globe. Kavanagh's portrait of Conor McGregor - who he has seen in his lowest moments, as well as in his greatest triumphs - is a revelation.

What emerges from Win or Learn is a remarkable portrait of ambition, discipline, and persistence in the face of years and years of disappointment. It is a must read for every MMA fan - but also for anyone who wants to understand how to follow a dream and realize a vision.