George Michael is happy for people to profit from his stint in prison.

The troubled singer served four weeks of an eight-week sentence for driving under The Influence of drugs in September 2010 and admits he encouraged the inmates at Suffolk's highpoint prison to get his autograph in order to sell it on later.

He said: "The strange thing about it is the whole wing had been told they couldn't come anywhere near me for an autograph, I did absolutely every single one of them - and every staff member as well. I used to say, 'Go and get a bit of prison paper and then it will be worth something, especially years down the line - get a bit of HMS prison paper with a George Michael signature', so I used to do that."

The 'Careless Whisper' hitmaker - who is rumoured to have split from long-term partner Kenny Goss - admits he was boosted by the letters he received from other celebrities, including Sir Elton John, Boy George and his former Wham! bandmate Andrew Ridgeley, while he was behind bars.

He told BBC Radio 2 DJ Chris Evans: "Elton wrote to me in the nick, which was nice, and so did Boy George, he wrote me a lovely letter. We spoke a few days ago, and I got a letter from Paul McCartney, which was lovely. George got through to me on which I thought was fantastic. There's a service where you can pay £5 a letter to write to a prisoner you know.

"Andrew got through to me from regular channels."

George - whose former lover Anselmo Feleppa died of an AIDS-related brain haemorrhage in 1993 - admitted he is now "completely clean" of drugs and hinted his problems stemmed from unresolved grief.

Speaking about his prison sentence, he said: "I just felt it was a logical conclusion to a whole period of very confusing times for me. I've never done anything in my life that I was so ashamed of, and I'd done this thing repeatedly which I didn't understand. But having understood it, I still felt like I had a bill to pay.

"I was terribly ashamed, every time it happened. Even though it was a mistake, rather than a decision each time, I didn't understand why it wasn't hitting my subconscious hard enough to stop it.

"And then I went in to proper, proper therapy and I'm now clean, of anti-depressants as well. Though they are miraculous in situations, sometimes they can really cloak what's going on and for the first time I had proper therapy about bereavement without anti-depressants."