From the early 1990s the efforts to end the so-called Troubles saw a string of important political encounters, each sealed with the clasp of hands.
When Tony Blair first shook the hand of Gerry Adams in a private meeting in 1997, he was met by angry unionists who pelted him with surgical gloves. The meeting took place away from cameras, but when the then Prime Minister went into loyalist East Belfast he was greeted with jeers of "you've blood on your hands" and had to dodge protesters firing rubber gloves at him.
In 1995, the then US President Bill Clinton shook hands with Sinn Fein leader Gerry Adams on the republican heartland of the Falls Road.
The moment was captured on film and became a defining image of the peace process.
The woman many credit with building the peace talks that led to the Good Friday Agreement, former Northern Irish Secretary Mo Mowlam, extended the hand of friendship to all aspects of a bitterly divided society.
She wash happy to meet, in her words, 'anyone and everyone' and did just that.
She was successful in helping to restore the ceasefire and in an attempt to persuade loyalist paramilitaries to participate in the peace process took the unprecedented, and potentially dangerous step, of visiting loyalist prisoners in the Maze prison.
In 2007 there were gasps at the footage of Democratic Unionist Party leader Ian Paisley and Sinn Fein President Gerry Adams sitting elbow-to-elbow in a press conference to discuss power sharing.
There was also shock at the subsequent image of Martin McGuinness and the arch-unionist laughing together as they went on to firmly establish their Stormont government.
In 2008, the then First Minister Ian Paisley met with, and shook the hands of, then Irish Irish premier Bertie Ahern, as deputy First Minister Martin McGuinness looked on.
Later, when Mr Paisley's successor Peter Robinson was rocked by the scandal surrounding an affair between his wife and a teenager, the new unionist figurehead received support from Mr McGuinness.
It emerged that Iris Robinson was suffering mental ill health, and in a private meeting Mr McGuinness offered his backing at what was a time of extreme pressure.
"He expressed sympathy to me and put out his hand. I thought it would be wrong of me in those circumstances to do anything other than that."
The gesture was the first of its kind between the leaders who had previously clashed in public.
We do not know whether there will be a picture of today's handshake, or whether cameras will be allowed to witness the historic moment.
But the fact that it is happening is in itself an extraordinary gesture for peace.