Detectives hope a viewer will recognise the distinctive handwriting

They join other victims including Dame Diana Rigg, Nyree Dawn Porter, Moira Lister and Pan's People dancer Dee Dee Wilde.

The investigation is headed by London's Metropolitan Police.

Detectives said after the BBC programme that the appeal had also received a "fantastic response" from the public wanting to help catch the writer.

Detective Sergeant Shirley McGlone said the letters, often in airmail envelopes, were usually sent from Bury, Bolton, Wigan and Manchester.

Many people from those areas later rang in.

DS McGlone said it was the style of the handwriting in the letters that had drawn the biggest response.

"We've got some people calling in to say there may be some musical background," she said.

"Other people are suggesting it may be an American because of the spelling."

Most of the writer's victims are women who were at the height of their popularity in the 70s and 80s.

Detectives were first alerted when actress Ms Lister contacted police last December about the letters - then thought to come from a theatre fan.

While police believe the celebrities are not in any physical danger, they said the level of harassment amounted to a "psychological assault".

Ms MacGregor said: "This has gone on long enough, it's more than a nuisance and it's actually against the law."

Ms McGlone said she was interested to hear from anyone who had noticed someone buying a large quantity of airmail envelopes.

Anyone with information can call West End Central Police Station on 020 7321 8878 or Crimestoppers on 0800 555111.