A teenager with dreadlocks accused of a machete attack has had the case against him dropped - because police broke the rules.

The 17-year-old, from Edgware, was charged with attempted murder following a stabbing near McDonalds in Watford High Street.

The incident happened at 2pm on Thursday, March 8.

READ MORE: Man rushed to hospital after being stabbed outside town centre

After two police officers viewed the CCTV he was arrested.

But the teenager told them he was at his family's home in Watford, saying: "I ain't the only black person with long hair."

During the attack the 23-year-old victim was punched, a large machete was produced and he was repeatedly struck. He fell to the ground, crashed into a market stall and was chased for a short while into an alleyway, where he was found bleeding.

In hospital he was treated for a very deep wound to the left wrist that went through to the bone.

He refused to make a complaint to the police or give his name.

But this week, St Albans Crown Court found police had broken the rules of CCTV identification when arrested the suspect.

During five days of legal argument, defence barrister Mark Kimsey argued that evidence from officers who looked at CCTV footage in a control room at Watford police was unsafe.

They had not signed in and out of the control room and no contemporaneous record was kept of the officers' identification of the suspect.

In her ruling, Judge Marie Catterson said: the officers had made "flagrant and wholesale" breaches of the rules.

She said there had been a "total disregard" for the code on CCTV identification under the Police and Criminal Evidence rules.

She said asked for a transcript of her ruling to be sent to the Hertfordshire Chief Constable.

The situation regarding CCTV identification at Watford police station last March "leaves a lot to be desired," she added.

The judge said: "An important training issue about codes of practice on identification needs to be addressed urgently."

Prosecutor, Beverly Cripps offered no evidence against the youth on charges of attempted murder, an alternative of causing grievous bodily harm with intent and possessing an article with a blade.

A spokesperson for Hertfordshire Constabulary said: “This has been a challenging investigation which led to evidence being gathered and charges being brought by the Crown Prosecution Service.

“We will be seeking further clarification around the ruling and will conduct a review of the investigation and our procedures accordingly.

"It would therefore be inappropriate for us to comment further at this time.”