A retired grammar school teacher died after allegedly being pushed in the street in a row over Welsh independence, a court heard.
Peter Ormerod, 75, had “opposing views” with Hywel Williams, 39, over whether Wales should break away from the UK.
Swansea Crown Court heard the men argued when they left the pub in Burry Port, Carmarthenshire.
Mr Williams, from Grangetown in Cardiff, denies manslaughter, saying he acted in self defence.
Prosecutor Ian Wright KC told the court: “During the course of that Saturday evening they were seated, at one point, in close proximity to each other.
“The conversation between them at the table turned to Welsh independence and Welsh politics generally.
“Peter Ormerod and Hywel Williams had opposing views on these topics and expressed these opposing views – and there was something of disagreement between them in terms of the views being expressed.”
The court heard Mr Williams left the pub to go and check his phone with Mr Ormerod “at around the same time” when he walked out with the defendant’s mother.
Mr Wright said there was CCTV of the two men coming together outside a coffee shop a short distance from the pub.
“Peter Ormerod can be seen to approach Hywel Williams and point or gesture towards him,” he said.
“Following this the two men appear on the CCTV to move towards each other before Hywel Williams pushes Peter Ormerod to the chest.
“That push caused Peter Ormerod to fall backwards on the back of his head. Having hit the ground, having hit his head on the ground, Peter Ormerod did not move again.”
Retired maths teacher Mr Ormerod died in hospital four days later on 28 September last year having suffered traumatic head and brain injuries.
He previously taught at Queen Elizabeth’s Grammar School for Boys in Carmarthen, and at the Welsh language school Ysgol Bro Myrddin.