How do you catch a chocolate bar thief on a moving train? Fill the carriages with hundreds of hungry schoolchildren on holiday with a keen nose for chocolate crime.
Children on board the Crunchie Gold Rush Train, which left Dunedin yesterday at 10.45am bound for Hindon, were told a Crunchie bar thief was on board and it was their job to hunt him down.
If he was not found, they would miss out on chocolate treats.
Needless to say, the robber was caught and the children were filled to the brim with chocolate when they arrived back at the Dunedin station at 2pm.
Amy Telfer Chiles and Stephen Chiles had waited four years to take their children Anna (5), Josh (8) and Shyla (7) for their first trip on the annual Cadbury train ride.
The children learned of the trip only when the family arrived at the station.
''I told them it was dress-up-as-a-cowboy day. They kind of figured it out when we arrived at the train station.''
When the train reached Hindon, the children discovered a giant chest filled with Crunchie gold and they filled their bags.
The Crunchie thief was handed over to Constables Louise France and Kate Saxton, of Dunedin, when the train returned to Dunedin.
Harry Easton (7), of Dunedin, managed to hide 17 Crunchie bars under his seat and promised he would not eat them all himself.
''I will give a couple to Granddad.''
