A drunken husband who struck his wife in a shop received instant punishment when an incensed pal knocked him out, breaking his cheekbone.
The husband was floored with a punch and then kicked on his body to "teach him a lesson" outside the store in Welford Road, in the city, on January 21.
The assailant, Tomaz Chojnacki, 28, told a police officer, who saw the attack, that the man on the ground "has just hit a woman."
The man's wife also told the officer that her husband had hit her in the store, where CCTV footage showed her falling over with the impact of her husband's forceful slap during an argument.
Chojnacki, of no fixed address, was known to the couple and had been drinking with them earlier.
All three were the worse for drink, said Victoria Rose, prosecuting, at Leicester Crown Court.
She said the victim suffered a fractured cheekbone near his eye socket, a two-inch cut, bruising and swelling to his face and back.
Miss Rose said: "It was done to teach him a lesson for striking a woman.
"The defendant was so outraged by what he had seen."
Chojnacki admitted causing actual bodily harm.
He was given an 18-month community order, with supervision.
Judge Robert Brown said: "You can't take the law into your own hands and assault someone, even if you disagree with what they did.
"Although he was clearly wrong in assaulting his wife, it doesn't justify your violence towards him.
"I take into account your lack of previous convictions for any offences of violence and the fact you're engaging positively with those who are trying to help you in terms of accommodation issues and alcohol dependence.
"The constructive approach is with a community order."
Jacqui Callan, mitigating, said Chojnacki has since left the area and is staying at a friend's house.
She said: "He told me 'I know what I did was wrong but I couldn't allow this man to do that.'
"He accepts he went over the top."
The court was told that the husband had been charged with – and admitted – battery of his wife.
In a recent city magistrates' hearing, he was also sentenced to a community order, with a drug rehabilitation requirement.
