Met police chief warns over 'pleb' case arrest

A police officer who claimed that he witnessed the so-called "plebs" row in Downing Street involving the former Chief Whip, Andrew Mitchell, was not actually there - according to the Head of the Metropolitan Police.

The officer was arrested at the weekend on suspicion of misconduct.

The Mayor of London has told the police chief that he is extremely concerned that any suggestion of an alleged conspiracy is investigated.

Nick Robinson reports.