BELFAST, Northern Ireland – Queen Elizabeth II and a former Irish Republican Army commander offered each other the hand of peace Wednesday in a long-awaited encounter symbolizing Northern Ireland’s progress in achieving reconciliation after decades of violence.

The monarch and Martin McGuinness met privately inside Belfast’s riverside Lyric Theatre during a cross-community arts event featuring Northern Ireland musicians, poets and artists.

Media were barred from seeing their first handshake during an ice-breaker over coffee and tea. But the two shook hands again a half-hour later for the cameras’ benefit, documenting a moment that would have been inconceivable back in the days when IRA leaders were plotting to kill the British royal family. McGuinness’ Irish nationalist Sinn Fein party had never attended a royal function before.

Afterward, McGuinness said he had told her in Gaelic – a language neither of them speaks – “Slán agus beannacht” and told her this meant “goodbye and godspeed.” The latter word actually means “blessing.”

The 86-year-old head of state didn’t speak but kept smiling as she shared a stage with a man linked to the killing of her cousin Lord Louis Mountbatten.

Experts on Irish republicanism say McGuinness, 62, was the IRA’s chief of staff when the outlawed group blew up Mountbatten’s yacht in 1979, killing the 79-year-old and three others.

McGuinness quickly left afterward. “It went really well. I’m still a republican,” he said in response to a reporter’s question.

The queen – in Belfast officially to celebrate her 60th year on the throne with an open-air party attended by more than 20,000 royalists overwhelmingly from the Protestant majority – also received a gift from Northern Ireland’s unity government that McGuinness leads alongside a Protestant, Peter Robinson.

Their unlikely coalition is the central achievement flowing from Northern Ireland’s 1998 peace agreement and the IRA’s 2005 decision to renounce violence and disarm.

Irish republicans long had rebuffed invitations to attend British royal events that occur regularly in Northern Ireland. But analysts said McGuinness’ U-turn became inevitable once the queen made her first state visit to the Republic of Ireland in May 2011, where she won public acclaim and made generous gestures, including honoring Irish rebels who died fighting for independence from Britain. Sinn Fein’s leaders suffered sharp criticism for boycotting her visit.