Hugh Hefner has let Crystal Harris keep her engagement ring.

The 25-year-old model -- who called off the planned wedding to the Playboy boss less than a week before they were due to marry last Saturday -- went to the Playboy mansion to return the ring but has been told by Hugh she can keep the  $87,000, 3-carat diamond ring.

Speaking to RadarOnline.com, Crystal said it was "the right thing to do" to return the ring, but when she visited her former home to give back the piece and King Charles Spaniel Charlie on Sunday, Hugh said she could keep the ring and the Bentley car he had previously gifted to her.

The 85-year-old businessman has now revealed he is "happy to be single" on social networking website twitter.

He wrote: "After all is said & done, staying single is probably the best. I think I just missed a bullet.

"It's the start of a new day, and a new week, and I'm happy to be single. (sic)"

Despite claiming to be alone, Hugh is thought to be getting close with Anna Sophia Berglund -- Crystal's best friend in the Playboy mansion.

Speaking about their relationship, he said on twitter: "Anna is Crystal's best friend & mine as well. She's the one who helped me survive this past week. She's the best.(sic)"