Sinn Féin ended weeks of speculation this afternoon when the party president, Gerry Adams, announced his key partner in pushing the republican movement from violence to constitutional politics would meet the Queen.
The handshake will take place at a cross border charity event in Stormont next week during the Queen's two-day visit to Northern Ireland as part of her diamond jubilee tour around the UK.
Speaking after a special meeting of Sinn Féin's leadership, Adams said it was a significant initiative.
Adams said the forthcoming encounter between McGuinness, the one time head of the IRA, and the Queen, who commands Britain's armed forces, was part of Sinn Féin's outreach toward the unionist community.
He said the move reflected Sinn Féin's "genuine desire to embrace our unionist neighbours".
McGuinness received support for the royal handshake from a former enemy in the loyalist Ulster Defence Association, Jackie McDonald The leader of the UDA and one time loyalist prisoner said the meeting represented a step forward.
Up until now Sinn Féin has boycotted events involving the British royal family who during the Troubles were regarded as strategic targets by the IRA. In 1979 an IRA bomb killed Lord Mountbatten on his boat off the Co Sligo coast in the Irish Republic.
According to former IRA commander turned informer Sean O'Callaghan, he thwarted an IRA operation to kill Prince Charles and Princess Diana at a charity pop concert in London's West End in the early 1980s.