Many people have dreamed of being cheek to cheek with Rufus Wainwright.

That situation came dangerously close following his last Edinburgh concert in December 2012.

While standing backstage following a small role in the Bacchanalian finale (dancing and shaking a giant bunch of grapes) he came off stage and discarded a flimsy toga, meaning his impressive tush was inches from my face. Unsurprisingly, it is an image that is difficult to forget.

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Thank goodness we have many other things to talk about, including Vibrate - The Best Of Rufus Wainwright, a collection drawn from the past 15 years of releases.

He is in California, primarily to celebrate the third birthday of Viva Katherine, his daughter with Lorca Cohen, but also to work on film projects that might see him in front of the camera as well as on the soundtrack. He says the smell of French toast is wafting through the apartment, making him hungry, so he is obviously not on an LA diet in preparation.

It is almost three years since the release of House Of Rufus, a lavishly presented boxed set of every CD as well as rareties, demos, collaborations and DVDs. Playing to his famous lack of modesty, the suggestion that House Of Rufus was his "best of" gets a blast of his unusual laugh - think cheery Woody Woodpecker.

"House Of Rufus was really more a chance to flush out things that were still lying around, but dying to make an entrance. The Best Of is really a more calculated review of my pop life.

"There are a few reasons for doing it now. I can't really tour a new pop record at the moment. I want to spend more time with my child, I am working on some movie projects, and about to start the second opera, so it is a good time."

It is also the last album with his current label Universal. He was the first artist signed to Dreamworks in 1996 (sold to Universal in 2005) and was given time and a pretty open budget to record the first, self-titled album.

Despite the critical acclaim and popularity of live shows, none of his albums have reached the Top 40 in America. Europe is different, with two top five albums in the UK, but still no dent on the singles chart.

"It's definitely a Best Of - it can hardly be a greatest hits! All the labels I have been on have been owned by Universal, so it makes practical sense to get the songs together now. And it is good to have a package to give to someone to say, 'This is Rufus, top to bottom, enjoy the journey!'."

The first draft of choices was put in the hands of past collaborator Neil Tennant and his trusted publicist Barbara Charone, the subject of a song on his last album. "I came in and made the decisions after that. My husband Jorn also had his say and, being honest, everyone has their favourites but there is only so much space."

There are a limited number of shows soon, including Edinburgh's Usher Hall, but being a solo show there will be no repeat of the showstopping finales that have seen him dressed as a fairy with thigh-high striped socks, crucified while singing Gay Messiah, and in full Judy Garland Summer Stock mode for Get Happy. And in a barely-there toga and laurel wreath last time round.

"Nothing major is planned, but often something comes up at the last minute that completely ruins my reputation."

It is a rare solo outing, the last being the tour accompanying the Songs For Lulu release that came in the almost immediate aftermath of his mother's death. Played as a song cycle with a request for no applause in between songs, the tour's visuals of Wainwright's blinking eye were created by Glasgow video artist Douglas Gordon. The pair developed the project, and now it forms the largest part of Gordon's latest exhibition Phantom.

This tour will see more conventional solo shows, with Lucy Wainwright Roche, daughter of Rufus's father, Loudon Wainwright III and Suzzy Roche, joining her brother.

From a Turner Prize-winning artist to the self-styled king of light entertainment, some have been scratching their heads about the recent collaboration with Robbie Williams. The connection is songwriter Guy Chambers, whom Wainwright first worked with as part of the BBC2's Secrets Of The Pop Song. The result of that collaboration WWIII is featured on the Best Of, as is another co-write, Me And Liza.

"I love working with Guy - we're very swift. He also understands the order of things. By that I mean I am the one that needs to go out and sing the song, so I am slightly more important (laughs), but I need to be open and respectful in terms of what he brings to the table. We have a good chemistry in that way."

There will also be further releases with Robbie Williams. "Even though the next big project is the new opera (based on the life of Emperor Hadrian) and releasing a recording of the first opera, Prima Donna, I in no way intend to abandon the pop career. The plan is to get some great songs together over a period of time and I hope by the time it is ready there will be a very, very hungry public."

There is no doubt he becomes particularly animated when talking about his favourite classical pieces and arias, as he did recently on Radio 3's Private Passions. "That was great. It's always good to do things like that and reflect on music that inspires you. I have not done Desert Island Discs yet though. I would like to do that. Let's put that thought out there..."

Home is now Montauk in New York state. "We have a beautiful home on the ocean, but also a place in Toronto as Jorn does most of his work there now. We also have a tiny apartment in New York. I need to sell a lot of records to continue this mad life."

The talk of New York and how artists can be allowed to be almost anonymous in the city leads to the tragic death of Philip Seymour Hoffman.

"He was a wonderful man and came to a few of my shows. We did hang out. He was absolutely the best actor of his generation."

With his own well-documented addiction problems behind him, Wainwright says of heroin: "That's a drug that ... really, you don't want to go there."

There seems to be a flirtation with acting but "I think if you are an actor you focus on that wholly. That being said, if I was offered a role that I could relate to and was not too much of a jump, it might happen. I would want to be good though ... I could never be Philip Seymour Hoffman good, but I would want to do interesting work."

During the spring tour he will head east to the Baltic states, Czech Republic and Poland for the first time. "That is exciting, casting the net a bit wider. If they are as loyal as Scotland has been, it will extend my career for a good while," he jokes. He laughs a lot, much happier and relaxed than in previous interviews.

So, finally an admittance to being one of his hedonist grape shakers during the last Edinburgh show, prompting, "You were great!" So, who knows, maybe acting is where his future lies.

Vibrate: The Best Of Rufus Wainwright is released on March 3. He plays Usher Hall, Edinburgh, on March 5