A father of two was punched to the ground and killed in an unprovoked attack as he tried to intervene in a disturbance outside a pub.
Vincent Greaves, 25, was jailed for four-and-a-half years over the senseless violence he used towards towards Richard Davies, 52.
A court heard how heavily-built Greaves struck him hard in the face as the older man tried to prevent further violence being used after the incident spilled out onto the street.
CCTV captured the sickening moment Mr Davies was punched and struck his head on the ground.
Graves was then caught on camera placing Mr Davies in the recovery position before fleeing with his friend.
Mr Davies died four days later in intensive care at Leeds General Infirmary after suffering “unsurvivable” brain injuries.
Leeds Crown Court heard neither Mr Davies nor Greaves had been involved in the initial incident inside the Aviator pub, in Guiseley in the early hours of May 31 this year.
Paul Mitchell, prosecuting, said the “catalyst” for the incident was a man called Jason White who had gone into the pub and began behaving aggressively.
He pushed a man to the floor before being strained by Liam Hancock and other people inside the pub.
Mr White continued to be aggressive and threatened people with a bottle before being ejected.
The court heard Mr Hancock, a friend of Greaves’s, took exception and followed White.
Greaves then joined his friend and were caught on camera running after Mr White and knocking him to the floor.
Mr Davis, who had been watching the incident from outside the pub, then approached the men.
Mr Mitchell said: “As he get there, he said words to the effect of ‘what are you doing that for.
“As Mr Davies approached Greaves, Greaves turned towards him and, without any hesitation, stepped forward to meet him and punched him very solidly to the face with his first.”
Greaves, of St Helens Way, Ilkley, pleaded guilty to manslaughter.
Ian Brooks, mitigating, said: “He struggles to understand why he behaved so out of character.
He made a terrible error of judgement. He has a high degree of remorse.”
Jailing Greaves, Mr Justice Males said: “The consequences of your actions were as devastating as they can be. I have read the victim personal statement by Mr Davies’s widow and it makes heartbreaking reading.”
Detective Inspector Paul Hobson, of Leeds District CID, said: “Richard Davies’ death was the result of a completely unnecessary outburst of violence by Greaves and clearly illustrates the terrible consequences that throwing just one punch can have.
“Mr Davies’ family are understandably devastated at their loss and our thoughts remain with them at this time. We hope they can take some small degree of comfort from knowing the man responsible has now been sent to prison.
“We hope this case will serve as a stark reminder to people of the tragic consequences that just a moment of violence can have.”