What's it like to hold a diamond worth more than $60m?

The Lesedi la Rona diamond is the size of a tennis ball and was discovered last November in a mine in Botswana. It was offered for sale at an auction at Sotheby's in London but didn't make its reserve.

No rough diamond of this size - 1,109 carats - had ever been offered at a public auction before.

William Lamb, the CEO of Lucara Diamond Corporation - which owns the mine where it was found - described the sensation of holding the enormous stone to Duncan Barkes on the Up All Night programme.