A stamp showing a triumphant Scotland team lifting the World Cup in 1978 is among the rare treasures to be displayed at a new post office museum.

Although the prediction never came true, and the stamp was never issued, the Royal Mail commissioned it before the tournament in case the Scots came home with the trophy.

Other curiosities set to be on show at the exhibition in the Mount Pleasant site, off Farringdon Road, Clerkenwell, include a sheet of stamps depicting an ageing Edward VII and telegrams from the Titanic on the night it sank – as well as the Mail Rail ride; a disused underground train track designed to move letters across London.

All these postal gems came to light as part of a Parliamentary debate over the future of the proposed £22million redevelopment of the museums.

Speaking in the House of Commons, Emily Thornberry MP for Islington South and Finsbury, said: “There is a remarkable history kept within the post office archives and the public haven’t been able to see these treasures since the old Museum, near St Paul’s Cathedral, closed in 1998 and have never been allowed to see the secret railway running under my constituency and many others.

“There is huge excitement from people who are interested in the industrial heritage of Britain in the 20th century, and they will be able to ride on that railway underneath the streets of London.”

The British Post Office Museum and Archive (BPMA) – are in the final stages of securing a Heritage Lottery Fund grant and have so far managed to raise all but £500,000 of that total, despite initial funding setbacks in 2013.

The government has donated only £70,000 to the development fund, something Ms Thornberry described as ‘pitiful’, saying: “such an important historic and social archive as the BPMA deserves a little more than £70,000 from the £2 billion sale of Royal Mail.”

The new museum is due to open in 2016 and is currently awaiting planning permission from Islington Council.