A rare bright yellow diamond weighing more than 110 carats - roughly the size of a woman's thumb - has gone on display in London's Natural History Museum.

Strongly coloured diamonds are rare enough, but the Cora Sun Drop, mined in Africa, is one of the biggest of its kind in the world.

Colour in diamonds, caused by the presence of other substances or structural defects, is usually much weaker.

Minerals curator Alan Hart explained how compared to standard diamonds - "small carat stones, colourless, white - this one is exceptional".

He added that, to the Museum,"the real value with these gems is that they're exceptional, they're one-offs".