On a cold November morning in 1983, armed robbers targeted the Brinks Mat security depot at the Heathrow International Trading Estate. Following an extremely brutal military-style raid, the gang got away with over £26million of gold. The robbery - the country's biggest and most notorious - caused the price of gold to soar and sent ripples through the criminal underworld. This programme hears from police officers who followed the increasingly complex case, as it pieces together the legacy of the heist