An unemployed plasterer killed a banker because he was "laughed at" and called a "half-chap", a court has heard.
Trevor Timon hit Oliver Dearlove while he and his friends were talking to a group of women in Blackheath, south-east London, in August 2016.
Mr Timon told the Old Bailey he was not trying to achieve anything by punching Mr Dearlove but had simply felt annoyed.
The 31-year-old, from Plumstead, admits manslaughter but denies murder.
Mr Dearlove, 30, who lived with his girlfriend Claire Wheatley in New Eltham, died within 24 hours of being attacked.
Giving evidence, Mr Timon said he had met a close female friend and three other women in Morden's nightclub for a birthday celebration.
He said he bought a bottle of champagne, of which he drank two glasses, and was "happy", not drunk, when he left the club with the women to go home.
He told the jury he walked up to one of the women "to tell her to hurry up" and then got into an argument with Mr Dearlove and his friends.
"One of them said 'she's with the half-chap'. They were laughing at me really, that's the way I took it," he said.
He said he then told one man "If you don't get out of my face I will knock you out" but meant it as "figure of speech".
Mr Timon told the court the victim did not make any comment about him but appeared "ready to fight".
When asked who was the first person to do anything physical, he said he was and that Mr Dearlove "just fell".
He said he was "shocked" to later hear the banker was taken to hospital, and went straight to a police station a couple of days later after returning from a trip to Ireland.
The case continues.