The fabled tunnels are said to have been used by Irish Chieftain, Owen Roe O’Neill to negotiate with the Parliamentarians during the ‘forgotten’ siege of Derry in 1649.

Now, centuries after the passages were sealed, there have been calls to open them up as a major tourism draw to the city.

Former Navy Commander Peter Campbell, of The Honourable The Irish Society - who can trace his family history to the architect of Derry’s walls in the 1620s (Peter Benson) - has appealed for the passages to be promoted as part of the city’s rich heritage.

“What I do think is we ought to open them up because everyone loves a secret passage. I think it would be terrific have it opened up - it would have great tourist potential.”

A spokesperson for the Northern Ireland Environment Agency’s Built Heritage department, which has guardianship of the walls, confirmed that there were many reports of “siege tunnels”.

However, she explained that many are in “private ownership and in variable condition”, making it “difficult” to open them to the public.

However, the NIEA is currently looking at making one tunnel more publicly accessible - the Sally-port which runs through the walls in the area of St. Columb’s Cathedral.

“NIEA and Derry City Council have recently been giving consideration as to how this important part of the history of the walls can be made more accessible for the public and would hope to address this issue in the near future.”