Inside the secretive warehouse housing a million works of art

Around a million works of art are hidden in the secretive Geneva Free Port.

Free ports - tax-free facilities for goods in transit - are springing up across the globe as specialist warehouses to store fine art and antiquities. They're being called "the greatest museums no one can see" - or the "weak links" in the fight against illegal trade in works of art, which helps to fund terrorist activity.

But the Geneva Free Port's new chairman is determined to bring about change by getting rid of so-called "undesirable tenants". BBC arts editor Will Gompertz has had rare access to the complex.