When a cyclist dies just nine minutes into a time trial on a dual carriageway, a van driver’s arrested. But a single mark on the road surface raises more questions than answers. BBC Cymru Wales #CrashDetectives #Crash #Investigation #Police #Detective The Crash Detectives: Every collision leaves a mark. Inside the cordon with Gwent Police's dedicated forensic teams, from crash site to custody suite, as they work to get justice for grieving families. | BBC