Who knew that the first-ever adhesive stamp, the Penny Black, would not only instigate a communications revolution but also a much loved global hobby?

It is estimated that there are 60 million stamp collectors worldwide. Stamp collections and the passion for stamp collecting have been passed down from generation to generation and they now form part of our history.

But what makes a stamp iconic for the collector? Is it the design, the story behind the stamp or simply the value?

Take a look at some of the most sought after and valuable stamps from the UK.