ancient, uniforms are permitted from time to time but the rules keep changing. Problem with the modern, comfy wear, is that it does not look like military uniform and is not smart.
If it is DPM the only way to differentiate is to see if the guy is wearing trousers, top and boots with the boot polished. Too many ponce around in designed DPMs. Some time ago, not that long, I saw a pretty young thing in a designer NBC Mk 3 NBC top.
This was a real designer item and not a functional NBC top. It was in shiny green fabric, like mine, identical hood and toggle, like mine, same map pocket but pukka nylon lining.
No wonder Joe Public is confused.
Gone are the days when your matelot stood out at Crewe station with his pusser's suitcase.