Pornography is now more easily accessible than ever before - it's a click away on the internet. And many men are finding their everyday relationships in peril because of their porn addiction. This documentary examines the problem and explores growing evidence that there is a chemical basis for the condition, uncovering the human costs of porn addiction along the way.

Graham was addicted to pornography he found on the internet. Not just any porn. Graham spent months looking at sites containing material on death by asphyxiation. He ended up strangling a young teacher in Brighton and kept her body for a month in a self-storage lock-up.

It's not just extreme cases like this, though. Hard-core pornography is now more easily accessible than ever before. And thousands of men are finding their everyday relationships in peril because of their porn addiction.

Like Eldon. He's never had a steady girlfriend and finds sex with a woman deeply disappointing after pornography. The programme follows him in his attempts to kick the habit. He tries to give up porn for a week. He undergoes hypnotherapy and attempts a blind date, but will he kick the habit that means he can't relate to a woman normally?

Warren is further along in his addiction than Eldon. After compulsively watching porn, he finds women on the internet who - unlike his partner - are prepared to act out the fantasies he's been watching. Duncan's addiction got him sacked from a top job in New York and saw him to blow a $2 million inheritance. Fuelled by cocaine, he'd watch porn and then call up prostitutes.

Hope may be at hand though as scientists have found that pornography is addictive. It taps into the same dopamine pathway in the brain that cocaine uses. And just like any drug, tolerance to it builds up, so bigger doses are needed to achieve the same effect.