Envelope with first ever stamp, sent to Northumberland in 1840, could fetch $2.5m at Sotheby's auction

The unique item was mailed to Northumberland with a Penny Black, the first ever adhesive postage stamp, on May 2, 1840, which was the day after the stamps were first sold and four days before they officially entered public use.

The envelope was then turned inside out and re-posted on May 4, this time making use of the fact that it was a Mulready envelope, a prepaid postage wrapper that also held a value of one penny.

Auction company Sotheby’s expects the item to fetch between $1.5m and $2.5m, nearly £2m, when it goes under the hammer in New York on Friday, February 2.

Richard Austin, Sotheby’s global head of books and manuscripts, said: “This unassuming envelope marked a significant leap forward in the history of human communication.

“Surviving over 180 years, the ornate Mulready envelope sealed with a Penny Black revolutionised the way people from all walks of life correspond, exchange ideas, share news, and express themselves.

“At the dawn of the AI age, this remarkable object speaks to our innate human desire for connection and the ways in which it has evolved to new heights in the two centuries since.”

The letters contained within the envelope have been lost to time and remain a mystery, but the postal markings show it was first mailed to William Blenkinsop Jr, the 35-year-old manager of Bedlington Iron Works.

It is theorised that the letter was from William’s brother John, who lived in the south of England at the time, but historians cannot be sure.

When the envelope was posted for a second time it was addressed to Mr. Blenkinsop, Dalston, Carlisle. This is thought to be William Jr’s father, William Sr, the owner of a prosperous cotton mill in the area.

This item is the only combined Penny Black and Mulready cover known to exist.