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Spices have been traded in the southern Indian city of Kochi (Cochin) in silence for centuries.

Traders use hand gestures and only the buyer and seller will know the final price agreed.

Kate Humble is on a journey learning how spices have shaped the modern world, and tried to learn the Indian hand signs herself.

Spice Trail is on BBC Two on Thursdays at 2100GMT from 17 February, 2011. Or catch up afterwards on BBCiPlayer