IPSWICH: It cost only one old penny to post – but it is now one of the rarest and most valuable envelopes ever sent to the town.

This rare piece of postal history, originally sent to trail-blazing agricultural engineer and inventor James Ransome, is set to fetch up to �28,000 at an auction next month.

The illustrated pre-paid one penny envelope – known as a Mulready after its inventor and designer, Irish artist William Mulready – is now particularly valuable.

That is because it was posted on May 5, 1840 – a day before it should have been sent on the official launch of the Mulready and Britain’s first adhesive postage stamp, the Penny Black.

And that wasn’t the only mistake. For the mystery London sender of the envelope – whose name is unknown because the letter originally inside the envelope is now missing – also used the wrong Mulready.

Something was enclosed with the letter, so a tuppenny Mulready printed blue on cream paper (costing two old pennies) should have been used, rather than the penny Mulready printed black on cream paper.

That error cost the envelope’s recipient, James Ransome, tuppence – a penny for the excess postage and a penny fine.

The handwritten “2” on the front of the envelope confirms that there is tuppence extra to pay. The Ipswich Mulready also features a third error – it has no cancellation mark.

It should feature a Maltese Cross cancellation mark on the figure of Britannia. The Ipswich Mulready safely reached its destination, because Ipswich was considerably smaller in 1840 – about a fifth of its current size – so postmen knew where to find the well-known Mr Ransome.

The envelope is so rare that experts know of only nine other May 5 Mulreadys. It is now expected to fetch between �25,000 and �28,000 at auctioneers Spink in Bloomsbury, London, on May 11.

But even with those hefty pre-sale estimates, it is not the most valuable Mulready. Next month, Spink are alsoselling a Mulready featuring 13 Penny Blacks that could sell for up to �125,000.

n Do you have a valuable piece of postal history? Call The Evening Star newsdesk on 01473 324788 or e-mail starnews@eveningstar.co.uk