Judge told a Forest Gate-based policeman that using the “N” word to a black suspect was “completely unacceptable in a civilised society”.

Judge Gledhill, at Southwark Crown Court on Thursday, went on to formally discharge Pc Alex MacFarlane of racially aggravated intentional harassment or distress,

The judge referred to Pc MacFarlane’s “momentary loss of judgment” during the London Riots last year.

Offering no evidence in a re-trial after a jury failed to agree last week, Duncan Atkinson, prosecuting said another hearing would be unlikely

The judge said the word “n****r” used against Mauro Demetrio was made “in the heat of the moment”.

Mr Demetrio was “angry and agitated” because of abusive language aimed at him earlier when Mr MacFarlane was not present.

Pc Alex MacFarlane, 53, was recorded on the suspect’s mobile phone telling him: “The problem with you is you will always be a n****r, yeah?’ after he was handcuffed in the back of a police van.

He then tells the 21-year-old: “You will always have black skin colour”, adding “Do not hide behind your colour, yeah” and “Be proud of who you are”.

The Judge said that having heard from them both it was clear to him that immediately having said the word, he realised what he tried to undo the damage.”

The Metropolitan Police officer, who admitted it was a “poor choice of words”, insisted he was trying to “calm down” Mr Demetrio who had referred to himself as a “n****r” first.

Mr MacFarlane pleaded not guilty.