Using the Terrorism Act to detain the partner of a Guardian reporter who covered US and UK security services was "legally sound", Scotland Yard has said.

It was responding to claims it misused its powers by holding David Miranda for nine hours at Heathrow Airport.

Mr Miranda is the partner of Guardian journalist Glenn Greenwald, who has published information from US whistleblower Edward Snowden.

The UK's reviewer of terror laws has said the length of detention was "unusual" and will meet police later.

Former Conservative MP Louise Mensch and computer scientist Jacob Applebaum debated the case on BBC's Newsnight programme.