The incident occurred on the night Wales played a football match against Argentina at the then Millennium Stadium.
Mr Adams was captured on CCTV in the city center at around 2pm, but was found lying on the floor with his face swollen and bleeding at 5.10am.
The attack involving three men is understood to have occurred around 2:30 a.m.
In 2018 a £10,000 reward was offered to help catch those responsible.
“This means quite a bit to Leon,” his mother, Angela Main, said at the time.
“He often asks: He wants to know why. That's harder. Why did they do it? We don't know.
“Is there a way you can literally stomp on a person's face so hard that it leaves footprints that match your shoe? I don't understand how you do it.”
2025-01-11 19:00:19
Leon Adams: Man dies after brutal attack 23 years ago
