A former karate champion left a man needing more than 100 stitches in a case of mistaken identity.

Robert Brennan turned vigilante after claiming to have suffered months of abuse at his home.

The 46-year-old, who put on a mask before the attack, decided to go out one morning in March this year armed with a hammer and a knife intent on retribution but instead he attacked an innocent man.

Brennan launched a violent assault on John Reid, 45, who was on his way to work at the time, while screaming: "You won't chase me out of my house".

Prosecutor Bernard Ablett said Brennan went out early on March 3 after donning a boiler suit, surgical gloves and a balaclava.

He armed himself with a hammer, knife and lighter fluid. Brennan was also clutching a bag with duct tape and flip flops inside.

The victim, who had never met his attacker before, has been left scarred as a result of his ordeal.

Brennan was jailed on Tuesday for four years and eight months after he admitted to a charge of assaulting Mr Reid to the danger of his life.

Brennan, who was a Scottish karate champion in the 1990s, will be supervised for a further three years on his release.

Judge Lord Beckett said: "Your attack will have lifelong consequences ... it has had a profound effect on him and his family."

Brennan struck months after moving into a flat into a flat in Rutherglen, South Lanarkshire.

The High Court in Glasgow heard claims Brennan had suffered "a campaign of harassment" at his home from youths. This was said to have had him living in fear of his life.

Police were never alerted but the court was told Brennan had contacted his local housing association.

It eventually led to Brennan taking the law into his hands as he went to hunt down those responsible for the hassle.

Mr Reid was heading to his car on the way to work from his own home nearby on the day of the attack.

The court heard that as Mr Reid got to his vehicle he was suddenly confronted by Brennan.

Mr Ablett told the court: "Brennan looked straight at him. After a moment's hesitation, he raised the hammer and struck Mr Reid on the head.

"Mr Reid tried to push Brennan away but he repeatedly struck out with the hammer and the knife."

The victim screamed for help as Brennan continued to lash out with the blade.

Neighbours heard his cries and ran out. They managed to drag a crazed Brennan off of Mr Reid, who was covered in blood, and pin him to the ground.

The victim slumped against a wall before police soon arrived. Mr Ablett said he needed more than 100 stitches and has been left with "extensive scarring".

Mr Ablett said: "He is left scared to come and go from his own house. He struggles to sleep and frequently wakes up in sweats during the night. He is worried about the safety of his family and does not feel he can remain in the house."

The court heard Brennan had been a Scottish Open karate champion in 1994.

Allan MacLeod, defending, said: "He said this was a campaign of harassment directed against him for two months. The consequences were severe for him. He was genuinely terrified that he was going to be attacked."

"He appreciates that the impact (on the victim) has been devastating and that what he did was wrong. He was a man, quite literally, at the end of his tether."