Operation Alice officers were tasked with investigating who passed information to The Sun and The Telegraph newspaper regarding the "Plebgate" incident, including whether the leak came from within the police force or from a third party.
They examined a police witness statement from the incident and investigated if there was a conspiracy between the officer and another party.
They also investigated claims made by Andrew Mitchell that police lied in the police log of the incident.
More top news
A court has ruled that the original coffin in which Lee Harvey Oswald was buried belongs to his brother, not the undertaker's that sold it.
Manic Street Preachers lyricist went missing nearly 20 years ago but mystery still surrounds exactly what happened to him.
Deputy Prime Minister admitted he wanted to hit David Cameron on more than 20 occasions on late-night chat show 'The Last Leg'.