Robbie Williams thought Lily Allen would back out of their duet.

The 'Go Gentle' singer revealed the Brit-Award winning singer agreed to record 'Dream A Little Dream' with Robbie for his new album 'Swings Both Ways' during a boozy night out with his producer Guy Chambers

Robbie claims Lily had no idea Gary was his producer but they struck up conversation over an impromptu performance of the 1931 classic.

In an interview with his biographer Chris Heath on Facebook, Robbie claims he thought Lily would change her mind when she sobered up the next day.

He explained: ''Lily thought that Guy was the piano player for the Groucho club and she said: 'Do you know Dream A Little Dream?.' He played it, she sang it and he said:'' I work with Robbie, do you want to come into the studio and sing It with him?'' She said yes - then you'd think that maybe she'd wake up the next day and go, 'Oh did I say yes? I meant no,' but she didn't. She came in and sang it with me.''

He added: ''She opened her mouth and the moment the first note came out it was a beguiling sound and I don't know, I sort of took a sigh out when she started singing. It was beautiful. She's got a great voice.''

Olly Murs also features on the album for a rendition of The Jungle Book classic 'I Wanna Be Like You', and Robbie claims they grew close when the 29-year-old star supported his 'Take The Crown' stadium tour earlier this year.

He said: ''I had a bond with Olly right from the beginning because I recognized a lot of me in him. He's a showman, there's not many around in the industry and he's very likeable and he sings really well too.''