The Brink’s-Mat robbery remains to this day one of Britain’s biggest and most audacious heists. Six armed men stole diamonds, cash and three tonnes of gold bullion from a warehouse close to London’s Heathrow Airport in November 1983. It’s now the subject of a BBC television drama, The Gold, which includes the claim that most gold jewellery bought in the UK from 1984 onwards will contain traces of that stolen gold. But how true is that? Tim Harford and team investigate, with the help of Zoe Lyons from Hatton Garden Metals and Rob Eastaway, author of Maths on the Back of an Envelope.