From sworn enemies to the "Chuckle Brothers", Martin McGuinness and Ian Paisley became Northern Ireland's most unlikely double act.
One was a former IRA commander, the other once stood up in the European Parliament to denounce the Pope as the Antichrist.
But remarkably, against all the odds, a deep friendship developed between these clashing figures that enabled the peace process.
In 2007, the DUP agreed to share power with Sinn Féin and Paisley and McGuinness became First Minister and Deputy First Minister.
In their first formal meeting as First and Deputy First Ministers, Paisley suggested sending a letter to the British secretary of state asking him to immediately vacate Stormont Castle.
McGuinness once revealed that this was one of the "most amusing episodes" for him.
"We did so in our first joint letter as First and Deputy First Minister. The British secretary of state and his staff were taken aback but did so.
"When we moved into our offices the following week, we discovered that they had taken everything with them, including the light bulbs."
What followed became a very public friendship. Images of the pair laughing and joking together earned them the nickname "The Chuckle Brothers".
"Our relationship confounded many. Of course, our political differences continued; his allegiance was to Britain and mine to Ireland. But we were able to work effectively together in the interests of all our people," McGuinness said after Paisley's death.
However, many in the DUP were unhappy with the friendship and, according to Paisley, he was forced to step down in June 2008.
In a wide-ranging interview on BBC Northern Ireland in January 2014, the former First Minister claimed he was edged out by senior figures in the DUP, after a canvass of the party found many MLAs were unhappy with his performance in the role, not least with his "chuckling" appearances alongside McGuinness.
After his death in September 2014, Paisley's widow Eileen revealed that McGuinness had been very supportive to the family during her husband's long illness and said their friendship had meant a great deal to her husband.
Speaking at an event in Belfast in October 2015, Mrs Paisley said: "During Ian's illness, he [Martin] contacted me.
"He would have texted me just to ask how Ian was, and say he was thinking about him.
"It was very precious to us as a family. It gave Ian a lot of happiness as well to know that he had left that impression with [him].
"His friendship with Martin McGuinness had meant something very special to him."
After Paisley's death, McGuinness himself spoke about their friendship.
"Despite our differences, I found him to be a charismatic and powerful personality. He always treated me and those who worked with me with respect and courtesy.
"The peace process and I have lost a friend," he said.