Sotheby's auctions a stamp worthy of Queen Elizabeth II's collection

A rare two-of-a-kind printed envelope, the other one of which is owned by the Queen, is up for sale

Who says stamp collectors are dull? Lady Mairi Bury of Mount Stewart, County Down in Northern Ireland, was living proof that collectors are among the most colourful people you could hope to meet.

Her lifetime was marked by a devotion to planes - Lady Mairi piloted her first aged 11, and her last aged 85 - and friendships with high ranking politicians, including the British Prime Minister Harold MacMillan.

In addition, she amassed what auction house Sotheby's has described as one of the finest collections of British stamps to become available on the private markets in 25 years. Following Lady Mairi's death last year, aged 88, around 2,185 lots from her collection will be sold by the auctioneer in London.

The stamp that started it all: the world's first postage stamp, the 1840 Penny Black

According to reports, the aristocrat began her collection at an early age; later building important collections of Cook Islands, Falklands Islands and Hong Kong philatelic rarities. Yet Great British stamps remained Lardy Mairi's main focus.

Total sales at Sotheby's auction, to be held on 24-26 November, are estimated to reach £2.6m. Highlights will include one of the finest known examples of the world's first ever postage stamp, the 1840 Penny Black.

Britain issued the Penny Black the year after it was discovered, by social reformer Rowland Hill, that it made more financial sense to price deliveries by weight rather than by distance and the number of sheets. This led to the passage of the Penny Postage Bill in 1839.

Until recently, the world record for a single mint Penny Black was $156,000 at a Danish auction house, in 2004. This was surpassed by an example sold by Stanley Gibbons for £250,000, in 2009 - so there will be high hopes for Lady Mairi's example when it appears at Sotheby's.

Other star lots will include a rare printed envelope which tells the story of Nemesis, an iron paddle steamer used by the East India Company in the first opium war of the 1840s. Making it even more impressive is that the only other known example of this cover is owned by Queen Elizabeth II.