On a spring afternoon in Brisbane's Musgrave Park, 18-year-old traditional dancer and amateur boxer Daniel Yock is drinking with his mates.

But when a police van arrives, the mood suddenly changes, triggering a dramatic chain of events.

Presented by Allan Clarke, Thin Black Line is a deep dive into what happened that day — according to the one eyewitness who saw it all unfold, speaking publicly for the first time in almost three decades.