Sir Cliff Richard has won the latest skirmish in a High Court battle with the BBC.
A judge has told BBC bosses to give the 76-year-old singer more information about how a journalist learned that he was being investigated as a result of a sex assault allegation.
Mr Justice Mann has ruled that BBC bosses must tell Sir Cliff whether the source of information was someone working on a wider Metropolitan Police inquiry into sex abuse allegations, an investigation codenamed Operation Yewtree.
Lawyers representing Sir Cliff wanted more detail about the source.
BBC bosses said they should not be forced to reveal more information.
Mr Justice Mann had analysed competing arguments at a preliminary High Court hearing in early May and has announced his decision in a written ruling.
The judge has said BBC bosses must provide a "proper answer" to the question Sir Cliff had asked about whether the source came from "within Operation Yewtree".
Sir Cliff has sued the BBC over coverage of a raid at his apartment in Sunningdale, Berkshire, in August 2014.
Lawyers representing the singer say he has suffered ''profound and long-lasting'' damage.
BBC editors have said they will ''defend ourselves vigorously''.
A spokesman said the BBC had reported Sir Cliff's ''full denial of the allegations at every stage''.
Lawyers have told how in late 2013 a man had made an allegation to the Metropolitan Police, saying he had been sexually assaulted by Sir Cliff at Sheffield United's Bramall Lane football stadium, in Sheffield, when a child in 1985.
Metropolitan Police officers had passed the allegation to South Yorkshire Police in July 2014.
Sir Cliff had denied the allegation and in June 2016 prosecutors announced he would face no charges.
Mr Justice Mann has overseen a number of preliminary hearings.
Any trial is expected to take place next year.
Sir Cliff had also sued South Yorkshire Police.
The judge was last week told how that dispute had settled after the force agreed to pay the singer "substantial" damages.