Martin McGuinness's meeting with the Queen will be a potent sign of mutual respect and part of the healing process from a generation of conflict, the head of the cross-border charity hosting the event has said.
Co-operation Ireland's patrons are the Queen and President Michael D Higgins. The charity builds bridges between the two communities in Northern Ireland and all parts of Ireland.
The charity's chief executive, former senior Northern Ireland police officer Peter Sheridan, said Wednesday's reception is an important step forward.
"It is something that demonstrates to ordinary people out there that we have gotten to the stage where we can acknowledge each other with respect. It does not mean that we have to agree," he said.
Everybody on the island of Ireland has been affected by the 30-year conflict, he added. "This is part of the healing process, of how do we make sure for the next generation of young people that we are not still revisiting these issues. It is our responsibility to fix those issues and not leave them to the next generation."
Since it was established in 1979, Co-operation Ireland has allowed groups from the two main religious communities in Northern Ireland and from both sides of the border to come together, learning about each other's traditions and culture to help build a society based on tolerance and acceptance of cultural difference.
The charity's board members include former Irish Taoiseach John Bruton and ex-US special envoy to Northern Ireland Paula Dobriansky. David Campbell, chairman of the Ulster Unionist Party, and former Irish rugby international Trevor Ringland, who has promoted grassroots reconciliation through his One Small Step campaign, are also on the board.
Mr Sheridan said Co-operation Ireland brought the Queen and President of Ireland together for an event celebrating its 30th anniversary.
It also helped organise the meeting between a former Irish president and the Queen in London, which led to the Queen's visit to Ireland last year and was acknowledged in her speech at Dublin Castle.
Its work includes Civic-Link, an education-based project which links schools on a north-south basis and gives students the opportunity to collaborate on projects based around citizenship and civic responsibility.