If you thought £1.35 for a first-class stamp was pushing the envelope, then brace yourself: a postage stamp described as the most valuable in the UK has been put up for sale for £650,000.

The Penny Red is coveted by collectors as an extremely rare example of an imprint that should not exist.

The Penny Black was the world’s first postage stamp, launched in the UK in 1840. The Penny Red replaced it in 1841 and was issued until 1879.

Billions of the stamps were printed in sheets of 240, and philatelists are unlikely to get into a flutter about most of them, but this used Penny Red is from plate 77, one of just 240 printed in the early 1860s before the authorities realised the plate was defective and destroyed it, along with all but nine of the stamps.

The stamp up for sale on Wednesday was originally joined to another, now held by the British Library. It first appeared in the records of a Manchester stamp dealer in 1920 and has since been owned as part of several collections.

In 2012, it changed hands for £550,000, while in 2016 another from the batch was sold for £495,000.

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The chief executive of Paul Fraser Collectibles, Mike Hall, said: “This stamp is legendary among collectors because it shouldn’t exist. While most people know the Penny Black was the first stamp, it’s plate 77 Penny Reds that send collectors into a frenzy.”

While £650,000 may sound eye-watering for a small patch of paper, it is far from being the world’s most expensive stamp. In 2021, an envelope bearing a Mauritius Post Office 1d red was sold for $11.2m (£8.7m).