(Cover) - EN Showbiz - Hugh Hefner didn't know "where [his] head was" when he asked Crystal Harris to marry him.

The 85-year-old Playboy founder and the 25-year-old Playmate were due to marry in a lavish ceremony at the Playboy mansion last month.

However, just days before the planned nuptials it was revealed Crystal had moved out and had called off the wedding, citing that the romance wasn't right for her.

Crystal has done a number of interviews stating her reasons for her decision since, including the fact that she wasn't comfortable being surrounded by a multitude of women in Hugh's mansion.

In his very first interview since the split with Piers Morgan Tonight, Hugh has revealed he doesn't know why he ever thought a relationship would work between himself and the young blonde model.

"I think that's a very valid question," he mused, when asked if he ever thought the romance could work. "Frankly, now, I'm asking myself the same thing. You know, where was my head?"

Hugh explained he made the commitment to Crystal in the first place because of shortcomings in his previous relationship with model Holly Madison.

The mogul insisted he thought it was the right thing to do.

"I made the commitment quite frankly because I felt like I had in a previous relationship with Holly, not been there for her in a way that she wanted me to be. And I just wanted to do whatever would make the relationship work. I was ready to settle down. I thought it was about time," he revealed.

"But on another level, I must say, quite frankly, the following Monday, I woke up and I was single, and I thought, this is the natural way. I should be single."

Hugh still struggles to make sense of his public break-up with Crystal. The infamous ladies' man believes the nail in the coffin was when the "pre-nup" was being discussed.

"[What went wrong?] That is the number one question and I don't have an answer for it. I really don't know what happened. I think in time, the rest of the story will play out," he explained.

"We took a trip to London... I think the real problems began a couple of months before the wedding was set when the lawyers got into it and we were talking about the pre-nup etc.

"We went to London about five or six weeks before. And things didn't seem the way they ought to be. I didn't see it coming. I truly didn't see it coming."

The former pair's nuptials were due to take place June 18. Hugh announced Crystal's "change of heart" just four days before the scheduled date.

Piers Morgan Tonight airs weeknights on CNN. (C) Cover Media