World wars have been fought in less time. It is four and a half years since Sheku Bayoh lost his life.

The 31-year , who had taken drugs, had been restrained by police officers responding to calls about a man seen behaving erratically with a knife.

Earlier this month prosecutors - after a lengthy probe carried out on their behalf by the Police Investigations and Review Commissioner (Pirc) - announced there would be no criminal action against any of the officers at the scene.

Mr Bayoh’s family and their solicitor, Aamer Anwar, saw this as a “betrayal”. But they were also angry for what they called an “undue delay”.

They are not alone in this. Calum Steele, general secretary of the Scottish Police Federation, who represents officers involved in the incident, also thinks investigations in to the case have dragged out.

“There are not many things about this case that we and Aamer Anwar agree on,” Mr Steele said. “But the amount of time this has taken is one of them.”

“The delay,” Mr Steele said, “has been extraordinarily frustrating.”

Police personnel living under the shadow of allegations have Mr Steele and the SPF to speak for them but - as serving officers - feel unable to get their side of the story fully across.

Mr Anwar blamed both Pirc and the Crown Office for delays.

Justice Secretary Humza Yousaf has now called a full public inquiry, which is likely to last longer than an anticipated fatal accident inquiry.

Asked to respond to Mr Anwar’s criticism of delays, a spokesperson for Pirc said: “We note the decision by the Justice Secretary to hold a Public Inquiry into the death of Sheku Bayoh on 3 May 2015.

“The Pirc was directed to investigate the circumstances of Mr Bayoh’s death by the Crown Office and Procurator Fiscal Service (COPFS) and submitted investigation reports to the COPFS in August 2015 and 2016.

“As this matter will now be examined before a Public Inquiry it would be inappropriate to comment further.”

A Crown spokesman also responded to criticisms of delay. He said: “The Crown appreciates that the time taken to conclude the investigation has been difficult for all those involved.”

“Following careful consideration and thorough review of all the available evidence, including submissions made on behalf of the family of the deceased, independent Crown Counsel has concluded there should not be a prosecution in this case.”