If you’re a fight fan – hell, even if you’re not – this HBO documentary about Johnny Tapia is pure gold.

Tapia was a world champion whose biggest opponents were the demons inside him. The punches he could handle, his love affair with cocaine he could not.

The film is two years old and I might have missed it but for a pal on Twitter (@GP_011) kindly sharing the link.

Tapia was blessed with a fighter’s mentality and a ferocious hook, but he was never far from catastrophe. Both his parents were murdered – there’s a great twist in the story, revealed in the film – and he grew up tough. Mi Vida Loco indeed.

A drug bust kept him out of the pro game for three years, but he still came back to win a world championship.

The footage is raw and gritty and offers a potent reminder of just how magnificent Tapia was. If he was this good as a drug addict, how great might he have been were he clean?

I was pleasantly surprised to see the names of 50 Cent and Lou Di Bella pop up as executive producers.

“The movie haunted me, both positively and negatively,” DiBella said. “Johnny’s life was like a Greek tragedy. He had so many demons.”

Di Bella and 50 Cent know boxing and the narrative consequently stays true to the sport and its less than savoury side.

The ending is wretched, but I won’t give it away here. Watch it. I dare you not to be moved.