Of all that was said and done in the immediate wake of Martin McGuinness’s death on Tuesday, Queen Elizabeth’s decision to sit down and write a private letter of condolence to his widow, Bernie, might take the cake.

Some context: In 1979, the Irish Republican Army blew up the queen’s cousin, Lord Mountbatten, who was really more like her favorite uncle.

As the chief of staff of the IRA and a member of the IRA’s ruling Army Council, McGuinness was personally involved in approving Mountbatten’s assassination.

And yet, five years ago, there was Martin McGuinness shaking hands with the queen at a charity event in Belfast, offering the strongest symbolic evidence yet that the British and the Irish had put their tortured past behind them.

The idea of the British monarch sitting somewhere in the gilded rooms of Buckingham Palace, writing a kind note to Bernie McGuinness, is the strongest symbolic evidence yet that Martin McGuinness deserves to be mourned and praised as a gunman-turned-statesman, as someone who took then saved lives. His redemption holds lessons for the rest of us.

McGuinness, 66, died in Derry after a short illness. His life’s narrative arc captured Ireland’s Troubles in all their savage loss and burgeoning promise. He joined the IRA when he was 18, having watched the Catholic civil rights movement that began in his native Derry literally beaten off the streets.

By the early ’70s, at age 21, McGuinness was second-in-command of the IRA in Derry and was part of an IRA delegation flown to London for secret peace talks with the British government. Those talks went nowhere, and after British soldiers opened fire on civil rights demonstrators in Derry on Bloody Sunday in 1972, killing 14 of them, Northern Ireland lost any chance to avoid a civil war.

Almost half of the more than 3,500 people who died in the Troubles were killed in the hyper-violent five years that followed Bloody Sunday, as the IRA took the fight to British forces and loyalist paramilitaries.

McGuinness was among the IRA’s most hawkish leaders but also one of the first to realize, by the mid-1980s, that the IRA and their enemies had fought to a bloody stalemate, in a conflict that neither side could win. With Gerry Adams, the leader of the Sinn Fein party, McGuinness began the long, slow process of persuading the IRA that the best and only realistic chance of bringing about a united Ireland was to end their armed struggle and reshape the republican movement as one dedicated exclusively to democratic politics.

It was not easy, nor without risk.

Richie Neal, the congressman from Springfield, knew McGuinness for a quarter century and was aware of the risks that McGuinness took, within his own community, in winding down the IRA.

“In politics,’’ Neal said from his Washington office, hours after learning of his friend’s death, “it’s easy to stand up to your enemies. It’s a lot harder to stand up to your friends. Martin stood up to his friends in the IRA and got them to move.’’

In 1997, during a mentoring process with the South African leaders who presided over the transition away from apartheid, McGuinness had something of an epiphany when talking to one of his heroes, Nelson Mandela.

Mandela explained that ending armed conflict was hard because you make peace with your enemies, not your friends. Beyond that, Mandela explained that making peace alone is not sufficient. Peace without genuine reconciliation just meant an end to armed hostilities. Reconciliation meant stability and a shared future, where former enemies could prosper together. That’s why Mandela went out of his way to embrace F.W. de Klerk, the last apartheid leader.

McGuinness took those lessons to heart. Perhaps more than any other leader in the Irish peace process, he was determined to demonstrate with his actions, not just his words, that he was committed to reconciling with former enemies after the Good Friday Agreement of 1998 ended the Troubles as we knew them.

His embrace of the Rev. Ian Paisley, the Protestant fundamentalist preacher and unionist leader he had long denounced as a bigot, was genuine. Paisley had in turn denounced McGuinness as a murderer. But they became a united front of civility and cooperation, a laughing, smiling duo nicknamed the Chuckle Brothers. As the first and deputy first ministers of Northern Ireland’s power-sharing government, Paisley and McGuinness became the most unlikely advertisement for letting bygones be bygones.

It was more than a calculated political stunt by both men: They genuinely liked each other, and they were both acutely aware that their ability to become colleagues and friends was a powerful, potent message in a country where reaching out the hand of friendship to former enemies could be interpreted as a sign of weakness or treachery.

After Paisley left government and later became ill, McGuinness checked in on him regularly. When Paisley died in 2014, McGuinness was shaken.

“I have lost a friend,’’ he said.

A few hours after McGuinness died, Paisley’s widow, Eileen, said she had lost a friend, too.

The last time I had a long conversation with Martin McGuinness, last year in Donegal, he was upbeat, optimistic about the future. He believed there would be a united Ireland. Maybe not in his lifetime, but before long. In the meantime, he said, “life is better for a lot of people.’’

McGuinness never apologized for being in the IRA, or for actions he took, and those actions certainly led to the deaths of many people. But he also met with and tried to find an understanding with those whose loved ones died at the IRA’s hands, just as he tried to explain the loss felt by those who lost loved ones to the British security forces and loyalist paramilitaries.

Colin Parry, whose 12-year-old son Tim was killed by an IRA bomb in England in 1993, was one of those who had one of those heartfelt conversations with McGuinness.

“I don’t forgive Martin nor the IRA,’’ Parry said. But he also believes McGuinness deserves credit for working so hard not just for peace but for reconciliation.

Paisley’s son, Ian Paisley Jr., offered a tribute that is as fitting an elegy for McGuinness as any: “It’s not how you start your life, it’s how you finish your life.’’

Martin McGuinness started his adult life believing that all power rested at the end of a pointed gun. At life’s end, he knew that mutual respect and being decent — to queens and preachers and everybody in between — was the most powerful thing in the world.

Kevin Cullen is a Globe columnist. He can be reached at cullen@globe.com.