The High Court was yesterday told other newspapers, and not just the News of the World, may have been involved in hacking the phones of Hugh Grant and his former girlfriend Jemima Khan.

Lawyers for the two celebrities were to court to try and force the Metropolitan Police to release any documents that might contain evidence that the private investigator Glenn Mulcaire was intercepting their voicemails while he worked for News International.

The police have custody of bags of documents and material gathered by the private investigator – who went to jail four years ago for hacking into royal-family phones for the tabloid – but no one has been allowed to see it.

 Mr Justice Vos ordered police to release the files and said Grant and Khan were entitled to see any documentation that might have been intercepted by Mulcaire and consequently used for articles in "the News of the World and other newspapers".

Vos also ordered the disclosure of former NOTW reporter Clive Goodman's notes used in his work as royal editor and gossip columnist.

The case could smooth the way for other celebrities, such as actor Jude Law, to gain more evidence as they seek damages from News Corp subsidiaries over hacking. Law's ex, Sienna Miller, has already settled a civil claim, winning about $150,000 and a courtroom apology by the tabloid.