A famous entertainer has won a High Court order banning a blackmailer from revealing details of a 'very serious' criminal offence he allegedly committed against her.

Mr Justice Warby said that earlier this month, representatives of the man, only identified as LJY, received a letter which gave no clue to the writer's identity but purported to be from a 'highly discreet organisation'.

It claimed that one of its 'clients' had alleged that LJY had committed a 'very serious' criminal offence against her some years ago but did not give any details.

It said the story was highly convincing and 'would be similarly convincing to the authorities or the press'.

A famous entertainer has won a High Court order banning a blackmailer from revealing details of a 'very serious' criminal offence she claims he committed against her

Giving his ruling in London, the judge said the letter suggested that the alleged offence caused the 'client' to lose out on financial opportunities and sought 'financial recompense' of £50,000.

A four-day deadline was given, with a discount offered for early settlement.

The letter said that if LJY did not pay, the details of the case would be released via news agencies and online resources.

It went on: 'In the current political and social environment we feel sure you will understand that this will have lasting damage to your career, your reputation and your personal life.

'This would in turn almost certainly hurt you more than the modest financial settlement we are seeking.'

Despite a warning to the contrary, LJY asked his representatives to contact the police and his solicitors.

The police believed it was a 'scam' and said that six identically-worded letters had been sent to individuals - although LJY was the first well-known victim.

LJY said he wanted to try to stop 'the person(s) unknown' from carrying out their threats as 'there is no justification for them' and that he had 'never been responsible for' any such alleged offence.

He described himself as 'angry and distressed that someone could do this to me'.

LJY's counsel, Jacob Dean, said that the letter was an obvious and blatant blackmail threat and may 'be only the tip of an iceberg'.

The judge ruled that the injunction was justified on the basis of harassment, misuse of private information and defamation.