Action man Dwayne Johnson spent more than three hours in the make-up chair every day, having the hair from a yak's testicles carefully stuck to his face for his new role as Greek demigod Hercules.

The Scorpion King star reveals he had to undergo a lengthy styling process before filming each day to make him look like the mythical hero director Brett Ratner had envisioned for the movie, but he made a surprising discovery one morning, when he enquired about where the hair had come from.

The typically clean-shaven actor says, "The beard hair... had to be put on, strips cut, inch high, quarter inch wide, piece by piece. I asked my Italian designer, I said, 'Matteo, what is this?' He goes, 'Oh, it's the hair from a yak'. It's very expensive, very fine hair... He was putting it on my face and I go, 'Well, what part (of the yak)?' and he goes, 'The testicles!'"

But Johnson confesses he was a big fan of the beard hair, adding, "It's the softest!"