When is a diamond really a diamond?

When it’s been formed miles underground a billion years ago, or when has it been created in a laboratory, under temperatures close to the heat of the sun? The answer is – both are true. They look and behave exactly the same, but they are very different in price.

The lab-grown diamonds are marketed as kinder to the environment, and they are far cheaper - and that’s led to concern about whether the two kinds have been mixed together, with man-made stones passed off as natural. So, what is the industry doing to give consumers confidence?

(Picture: Close up of man putting engagement ring on girlfriend. Credit: Getty Images)

Presenter: Lesley Curwen Producer: Barbara George