First penny black stamp could fetch up to £6m at auction

Launched in 1840, Sotheby's says the stamp is the most important piece of philatelic history to exist'

It was less than one square inch and cost just a penny but it launched a revolution in communications. Now the first penny black", the postal stamp bearing an image of Queen Victoria's profile, is expected to fetch up to 6m when it is sold at auction.

The stamp was a runaway success when it went on sale in 1840, allowing people to send a letter weighing up to half an ounce to any destination in the country for a flat rate of one penny. Eventually more than 68m stamps were sold.