The inquiry is also considering public interest immunity applications from MI5 and the MoD aimed at restricting its material at the hearing.

BBC: Derry Guildhall

The third set of appeal grounds also relate - according to the documents - to undisclosed information for which the UK Government had sought public interest immunity from disclosure.

BBC: Law chief 'deplores' bomber claim

The UK government's public interest immunity (PII) application to exclude sensitive information is being opposed by lawyers for Mr Litvinenko's widow as well as media organisations, including the BBC.

BBC: Litvinenko inquest: Coroner examines secret files