A violent bully has been jailed for killing a father of four who spent two years in a coma after being floored by a single punch in a “gratuitous, unprovoked” street attack.

Michael Broom, 50, was originally sentenced to three years in prison after admitting causing grievous bodily harm to Mark Haley.

Following Haley’s death last year, however, Broom also pleaded guilty to manslaughter and was sentenced at the Old Bailey to two more years behind bars.

Broom, a labourer known locally as a drunk, had picked on Haley near a Tesco store in Chessington, Surrey, at around 6pm on 21 August 2011.

Haley had brushed past Broom, who was perched on the back of a BMX bicycle being ridden on the pavement by a 14-year-old boy.

Broom then took his shirt off and punched Haley in the face, causing him to hit his head against a pole before falling to the ground.

The incident was witnessed by several members of the public and was also caught on CCTV, the court heard.

Haley, a former BT engineer who lived locally, was airlifted to hospital with a serious head injury which left him in a coma.

In August last year, the 53-year-old suffered an associated chest infection and died almost exactly two years after the attack.

He said his father was his rock and role model, and had taught him the importance of responsibility, hard work, manners and morals.

Haley’s widow, Joanna, wrote that she had been heartbroken to see her “bright, intelligent, quick-witted” husband reduced to a vegetative state.

The court heard that Broom had a string of 16 convictions, many of them related to his violent and aggressive behaviour while drunk.

Khalid Missouri, defending, told the court: “It is fully recognised this is an appalling, terrible tragedy and the defendant accepts and is remorseful for that tragedy.”

Jailing him, judge Richard Hone QC said: “You and Mark Haley met in Hook Way in Chessington. You were perched on the BMX of a 14-year-old. You were the aggressor and the victim was reported as polite and non-confrontational.”

Outlining the aggravating factors, he said: “First, this was a gratuitous, unprovoked assault. Secondly, it took place in the street with a 14-year-old and numerous other eye witnesses present at an ugly scene. Thirdly, the removal of your shirt indicated a determination for significant violence.

“One witness described you as ‘the local drunk’ and many of your convictions resulted from your alcohol addiction. You can reasonably be described as a violent bully and that categorised your behaviour that Sunday afternoon.”