PC Benjamin Monk was sentenced after being convicted by a jury at Birmingham Crown Court last week.

Monk, of West Mercia Police, tasered Mr Atkinson for 33 seconds, more than six times longer than the normal cycle, before kicking him at least twice in the head during a confrontation in August 2016.

Monk’s conviction is believed to be the first time in modern British criminal justice history that a UK police officer has been found guilty of the manslaughter of a black man, according to Inquest, which supports the bereaved following state-related deaths.

He is also believed to be the first police officer in 35 years to be convicted of unlawful killing over a death in custody or following police contact in England or Wales.

On Thursday, jurors were discharged from reaching a verdict on Monk’s partner Mary Ellen Bettley-Smith, who was accused of assaulting Mr Atkinson with a baton after he was tasered to the ground.

Jurors took more than 18 hours to reach unanimous verdicts on the manslaughter charge against Monk. They cleared him of Mr Atkinson’s murder.

The court heard the former Aston Villa, Sheffield Wednesday and Ipswich Town striker had been shouting in the street in the early hours of 15 August 2016 outside his father’s house in Telford and was demanding to be let in.

Monk fired a Taser three times – including a single 33-second discharge – and left two bootlace prints on Mr. Atkinson’s forehead, the trial was told.

The 43-year-old claimed to have acted in reasonable self-defence while “terrified” of Mr Atkinson, who had a heart condition, was undergoing dialysis treatment, and was smaller and lighter than the officer.

As well as the marks to both sides of Mr Atkinson’s forehead, a pathologist found 15 areas of “under-the-skin” bruising, including marks to his neck, shoulder, shoulder blade, flank, buttock, thigh, bicep, elbow, and shin.

In a statement after the jail term was imposed on Monk, Dalian Atkinson’s family said: “PC Monk used horrendous violence against Dalian, who was in an extremely vulnerable position in a mental health crisis and needed help. This was a callous attack and a terrible abuse of a police officer’s position of trust. He then failed to give a full and honest account of what happened, including at his trial. We are pleased that all these factors have been reflected in the sentence.”

Passing sentence on Monk, Judge Melbourne Inman QC told Monk “You have let yourself and the force down. Although they were difficult, you failed to act appropriately in the circumstances as they developed and you used a degree of force in delivering two kicks to the head, which was excessive and which were a cause of Mr Atkinson’s death. The obvious aggravating factor is that you committed this offence while on duty as a police officer. The police play a central and important role in upholding the rule of law in our society. The sentence must reflect the importance of maintaining public confidence in our police”

Prosecutors said Monk had exaggerated the threat posed by Mr Atkinson and lied about the events to justify excessive and unlawful force.

Prosecutors also said the officer lied about the number of kicks he had delivered to the former sportsman’s head by claiming he could remember only one aimed at his shoulder.

The trial was told Mr Atkinson, 48, went into cardiac arrest after being taken from the scene in an ambulance and was pronounced dead in hospital at 2.45 am – about an hour after he was tasered.

Rosemary Ainslie, who authorised the original charge against Monk as head of the CPS Special Crime Division, said: “From the medical evidence it was clear that if not for the excessive force used by Benjamin Monk then Dalian Atkinson would not have died when he did. Monk forcefully kicked Mr Atkinson at least twice to the head. The force used was unreasonable because it was not necessary to restrain and control Mr Atkinson who was prone on the ground.

“The jury rejected any claim that Mr Atkinson’s death resulted from reasonable self-defence in the line of duty. Policing is a difficult job and officers deserve our respect, but they are not exempt from the laws they uphold.”