Britain's rarest stamps to be sold

A set of 81 rare stamps whose distinguishing feature lay undiscovered for 40 years is to be sold at auction after researchers discovered their true worth.

The stamps, which include an issue celebrating post office technology and another on architecture, were released by the Post Office between 1969 and 1974 – including this set of churches from 1972 – as "Postal Notices" to inform staff what a forthcoming set would look like. In order to prevent fraud, each set was encased in a thick perspex block, concealing the precise printing method.

But researchers at Oxford University have discovered that, unlike normal stamps sold at Post Office counters, the encased stamps had been printed on rolls of paper that did not carry the shiny coating used in the official mail. As a result they are worth an estimated £500 each.

Andrew McGavin, of Universal Philatelic Auctions, which commissioned the research, said: "That instantly makes these 40-year-old stamps the rarest commemorative stamps in Britain."