Single pop heartthrob Robbie Williams has vowed never to marry, because he isn't capable of remaining faithful. The singer has dated sexy celebrities Geri Halliwell, Rachel Hunter and Nicole Appleton, but wants to stay single so he can make the most of his popularity with the opposite sex. The 32-year-old, who quit alcohol five years ago after undergoing rehab, says, "For the first two or three years of my sobriety I was desperate to be in a relationship because I thought it would fix me. "But if you're in a relationship you have to keep your d**k in your pants - and I'd struggle with that. "Now I don't want one, I look at every relationship and think, 'What's in that for me.'"