Colin Farrell reckons that he has “eight extra hours a day” since he quit alcohol.

The 36-year-old actor has been sober since checking in to rehab in 2006 and admits he was shocked by how much time he had wasted on his alcohol and drug addictions.

“I’ve got eight hours a day now that I didn’t have before, when I was drinking every day for 18 years,” he told Details magazine.

“It’s honest, it’s real. That’s quite simply the coolest thing.” The Dubliner also acknowledges that he was ashamed to admit that even the birth of his son James in 2003 didn’t make him clean up his act.

"When I had James, I made a decision not to change,” he recalls. “I literally said, 'I'm not changing! I'm gonna be his friend!' Like a ****ing 28-year-old drug-addicted drunk friend is exactly what my six-week-old son needs.”

Farrell spent most of his time lying to family and friends to cover up his excesses but says it was exhausting keeping track of his untruths.

"Oh, I wouldn't tell a truth all day," he admits. "If I'd had chicken and beans for dinner, I'd tell you I had steak and potatoes. No purpose, just habit.

"The amount of energy you have to put in and the amount of lies you have to tell to keep a drug habit alive, it's fairly significant. Your whole life is a lie."