Cilla Black didn't want to appear in her biopic.

The legendary entertainer - who is being portrayed by Sheridan Smith in the upcoming TV mini-series 'Cilla' - wasn't keen on the idea of making a cameo in the show as she didn't want to put her own mark on the production.

The series' writer Jeff Pope explained at a Q&A for the ITV drama at London's Soho Hotel: ''I think she wanted to let us do it and she didn't want to put a footprint on it.''

Jeff added that the 77-year-old presenter may have found it odd listening to Sheridan, 33, singing her songs on the set of the three-part drama.

He said: ''If Cilla came up to set and just had one line the idea of her standing there watching and Sheridan singing all of her songs, she would've turned around and gone away again.''

However, Cilla did meet up with the 'Mrs Biggs' star to give her some advice on playing the role and encouraged her to master not one but two singing styles in order to perfect the portrayal.

Sheridan explained: ''When she was singing in the Cavern Club [in Liverpool during the early years of her career] - Cilla told me this herself as well - because it was so loud you would just whack it out, those rock and roll songs.

''And then when she'd get in the studio with headphones on she realised she had this little soft voice as well so that's why she started doing ballads as well and that was kind of fun to play around with ... The soft voice and then the kind of Cilla honk.'' 'Cilla' premieres on September 15 at 9pm on ITV1.