McGuinness's steady hand will be missed as unionists will never find a more accommodating coalition partner
Peggy McGuinness was worried about her son. It was 1972, and she had found an IRA beret and belt in his bedroom. Martin had just given up his job and the newspapers were describing him as the officer commanding the Provos' Derry brigade.
"His father is a welder, his brothers are at the bricklaying and carpentry, but what will become of Martin?" she fretted. Mrs McGuinness needn't have worried. Her son ended up something that even in her wildest dreams she wouldn't have considered - deputy first minister of a state he had once vowed to smash.
I interviewed him shortly after his appointment and he stressed how determined he was to build a strong relationship with Ian Paisley, who had once demanded that the Sinn Féin leader be hanged.
Mr McGuiness brushed it all away. "I've called him a sectarian bigot, I think he's called me worse but I'll not repeat it!" he joked. The two old enemies clicked instantly because, despite initial appearances, they weren't polls apart.
Both were conservative family men who liked the simple things in life. "Although, I'm not quite as religious as Ian!" Mr McGuinness quipped. Both detested 'the devil's buttermilk'. "I've a glass of wine at Christmas dinner but never more than two. I'd rather sit in the house with a mug of tea," Mr McGuinness said.
Understandably, unionists initially hated him because of the numerous IRA atrocities conducted on his watch. But at Stormont, and in meetings with ordinary people in the community, he won many sceptics over.
"Call me Martin!" he declared at Stormont while other cabinet colleagues insisted on 'minister'. Security staff, porters and canteen workers - you would be hard pressed to find one who had a bad word to say about him personally.
Protestant civil servants who had worked closely with him were visibly emotional as he packed up his belongings before Christmas.
While Gerry Adams talked about the need to "break these b******s", McGuiness told the Sinn Féin ard fheis that unionists should be "loved and cherished".
During his time at Stormont, he bit his lip in a way that other republicans facing provocation from the DUP's wilder wing would never do. Indeed, his tolerance emboldened that party's leadership to the extent that they mistakenly believed that he would never press the nuclear button and collapse the Executive.
In interviews yesterday, Mr McGuinness spoke of how he wanted to spend time with his family, fighting his illness out of the public spotlight. That's entirely in keeping with what we know about him.
Although his four children are long grown-up, he told me that he would never have dreamed of spending the week in Belfast in order to avoid the 140-mile daily round commute from Derry. "I believe in going home every night," he said.
He has an exceptionally strong relationship with his wife of 42 years, Bernie Canning. Family is everything to him. As deputy first minister, he travelled the world. But he said that his most special trip was a private one.
"I took my grandson to Paris when Derry City played Paris St Germain. It was nothing to do with Sinn Féin or politics, just a family visit. We walked through the streets together and I thought ... this is so special."
Despite Mr McGuinness's illness and his amiable manner, which surprised many political opponents, he certainly shouldn't be sentimentalised.
Mr McGuinness's departure will leave a huge gap in Sinn Féin's leadership in Northern Ireland. In the Republic, the party is brimming with talent - Pearse Doherty, Peadar Tóibín, Mary Lou McDonald and Pádraig Mac Lochlainn to name but a few.
Conor Murphy was once the clear frontrunner to take over. Now he appears too dull for a dynamic political environment in which people want change.
Michelle O'Neill is emerging as the favourite. Her youth, gender, and lack of IRA baggage should appeal to a wide section of the electorate - at least for now. But she lacks the former deputy first minister's gravitas, and unionists will never find another more accommodating coalition partner than him.
Sinn Féin seems set for a good election. It won't be until the negotiations start and beyond, that the strong, steady hand of Mr McGuinness will be missed. Even the DUP may come to regret his departure.