The Democratic Unionist Party in Derry claims to have unearthed an historical royal manuscript which they believe settles once and for all the row over the official name of the city.
The manuscript, in antique book form, contains translations of royal charters granted almost 400 years ago which state the name of the city "shall for ever hereafter be and shall be named and called the city of Londonderry".
Yesterday's discovery came on the day when it was revealed that the nationalist-controlled city council had written to more than 170 non-governmental organisations, sports and community groups and business groups reminding them that under its policy the council only recognised the name Derry as being the official name of the city.
Among the groups which received the letter were the Londonderry Chamber of Commerce, the Londonderry Port and Harbour Commissioners and Londonderry District Sports Council.
Twenty years ago the council changed its name from Londonderry to Derry and nationalist councillors have maintained that that automatically changed the name of the city to Derry.
The city received five royal name charters between 1604 and 1689, but the second charter, granted by King James 1 on March 29th, 1613, is accepted by historians as being the most significant. That charter, a copy of which the DUP says it has uncovered, states that "the said city or town of Derry, for ever hereafter be and shall be named and called the city of Londonderry".
DUP Alderman Mr William Hay said the discovery of the royal manuscript proved legally and conclusively that Londonderry was the official name of the city.
"I just can't describe the anger which this move by the council to effectively force people to use the name Derry in correspondence with the council has caused among unionists. Any organisation which corresponds using the name Londonderry should be respected and left alone. The same goes for those who use the name Derry," said Mr Hay.
However, Sinn Féin councillor Mr Barney O'Hagan said the city needed to have one unambiguous brand name. "There is no republican agenda at work here. At present we use a plethora of names, trying to be all things to all people, and in doing that that gives an air of division.
"I don't think that claims by members of the Protestant community that the name Derry and the council's policy on the issue makes them feel alienated and unwanted stands up to any scrutiny at all.
"The unionists should be confident about their position in this city and we should all rally around that one name of Derry."