The family of a man killed while breaking up a fight is urging the police to reopen their investigation into his death based on evidence that emerged at his inquest.

David Joslin, 23, died just days after being punched to the ground while intervening in an argument in Old Church Road shortly before Christmas 2009.

Today, more than three years later, coroner Chinyere Inyama ruled he had been unlawfully killed after the punch caused him to hit his head on the ground, which proved to be a fatal blow.

Walthamstow Coroners Court heard evidence yesterday from witnesses who said Mr Joslin had intervened with his hands up in the air, but was still hit with a punch which could not be deemed to be thrown in self-defence.

Witnesses Barry and Michael Oliver, who claimed they were set upon by 11 or 12 people that night, said they did not remember what had happened.

Barry’s girlfriend gave a statement shortly after the incident to police saying that immediately after the event Michael had talked about hitting “anyone who came near him and saying he put a few on the floor".

Both brothers say it has been too long since the incident to remember properly.

Today the coroner ruled their evidence was “inconsistent and not convincing” but praised the evidence of witness Michael Butterworth, the first time he has been heard in court, who said he remembered the man who punched Mr Joslin wearing jeans and a cream top.

Michael Oliver denied that when shown CCTV footage by police he had agreed he wore a cream top on the night.

Father Phil Joslin said: “I will be writing to the CPS. I’d like them to review the case and for police to reopen the investigation and questioning of the people involved in the inquest into the evidence they’ve given.

“I feel there is a very strong case there which must be re-investigated.”

Coroner Inyama also found there were grave failures in the standard of care given to Mr Joslin by Whipps Cross University Hospital on the night he was admitted, when he was treated as a drunk despite having little to drink.

He was in a state of agitation consistent with brain injury and admitted because of an alleged assault, yet was left for seven hours to sober up.

He was also not given a CT brain scan until after 9pm, 19 hours since his 2.30am arrival, contravening national guidelines which suggest he should have received one by 4.30am.

However, the coroner ruled out that the treatment may have contributed to Mr Joslin's death after an expert testified that he would have died no matter what care he received.

Coroner Inyama said as a result of Mr Joslin’s death he is recommending changes to national guidelines to ensure staff always record pupil dilation – a sign of brain injury – because Mr Joslin’s were not noted.

Nor were pupil dilations in 80 per cent of cases a year after a review was meant to instigate change.

Mr Joslin snr said: “It gives us some comfort that things will change because of David’s death, and that the court found he was not drunk and in no way were his actions anything but peaceful.”

Barts Health NHS Trust said it has made improvements since Mr Joslin’s treatment and continues to do so, including emphasising the need to check intoxicated patients for brain injuries and improved awareness of national guidelines.