The first time I met Martin McGuinness was in the early 1990s in a hotel bedroom near the Border. Albert Reynolds was Taoiseah and he had asked me to take a message to him.
I conveyed the message and awaited the reply as he wrote in a notebook. Then he said: "I'll have to bring it back to the IRA."
I ventured that he could just pop into the en-suite bathroom, look in the mirror and come back out to give me the answer. He smiled, and then said: "We'll be back to ye." As he left, I remember thinking I could get on with him.
We always got on well and I always found him open, frank, warm and likeable. But let's be clear, he said himself that there were two distinct phases to his life.
I knew him only in his second phase when he was committed to resolving the political problems in Ireland by exclusively peaceful means, as his oath of office as a minister in the power-sharing administration required of him. I rather fear in his earlier phase - when he was active in the Provisional IRA - there were dark shadows and grim happenings.
He would never distance himself from that activity beyond acknowledging that loss and grief were experienced by all sides. This was at a time when the efforts of democracy and moderation were being undermined by violence.
But I have to say that when he committed to constitutional politics, that commitment was total. He transformed himself and worked with other parties and, crucially, the two governments to transform the political situation in Ireland. In that work, his ability to ultimately establish a rapport with people, especially adversaries, was a typical trait of his.
I engaged in serious business with him and others for more than a decade. During my time as foreign affairs minister, we had to deal with the first suspension of the power-sharing executive and the subsequent political work to achieve restoration.
There were detailed discussions on resolving the arms issue, and negotiating with the DUP, once it joined the process. Getting final agreement on the legislation for policing reform, as per the Patten Report, was achieved when Gordon Brown and I worked together as prime minister and taoiseach.
I recall with affection now the occasions when a sense of humour helped reduce the tension as tempers frayed, or political progress was stalled. There was an incident when Peter Mandelson was Northern Ireland secretary. He and I were meeting the party delegations one at a time regarding an impasse we had reached.
The Sinn Féin delegation got a poor reception that particular day. As they were leaving they said goodbye to Mr Mandelson, only to be greeted with silence. Mr Mandelson's dog, called Bobby, was sitting near the door. Mr McGuinness and Gerry Adams addressed the dog: "Slán, Bobby," they called out mischievously. I don't think it answered either!
Another time, I met the two of them with officials in Government Buildings. The taoiseach, Bertie Ahern, was unavoidably late getting to the meeting.
Martin was getting himself a cup of tea when Mr Adams very formally congratulated the Irish government for being just elected to a term on the United Nations Security Council. I quickly retorted: "Ah, you know yourself, Gerry, we're just trying to keep a few wars under control." Martin kept his back turned to the company but I could see he was having a good chuckle.
I also recall giving him a private "heads up" that president George W Bush was coming to Stormont in the following few days. I told him of the absolute necessity for secrecy. "Keep it tight," I said. He looked at me knowingly. "Don't worry, Brian. We're good at 'tight'."
I also believe his Derry origins marked him out as different from some of the republicans "east of the Bann". There was the personal warmth, and a lack of doctrinaire ideology. Political ecumenism comes easier to them in Derry. John Hume's insistence on the rotation of the mayoralty there, despite an in-built nationalist majority on the city council, set that political tone many years before.
Mr McGuinness was, in my experience, passionate about the peace process and keen to make it work. My first job as taoiseach in 2008 was to travel to an investment conference in Belfast where I was greeted warmly by first minister Ian Paisley and deputy first minister Martin McGuinness.
I was struck by the remarkable relationship between the two. Mr Paisley had crossed his political Rubicon and enthusiastically embraced a new reality. Mr McGuinness strove to reciprocate and share that new political space the then first and deputy first ministers were creating. Cynics in politics and the media reduced their partnership to " the Chuckle Brothers".
Incrementalism is often deemed the right option in politics. Slow, cautious change borne down by excessive process and bureaucracy.
What is absent from our politics currently in making the peace process a real success, beyond the absence of institutional and paramilitary violence, is to embrace the 'spirit' of the Good Friday and St Andrew's agreements. That means incorporating the generosity of spirit that all traditions are equally legitimate and must be given confident recognition, not just begrudging acknowledgement, by the other side.
Instead of condemning another generation to killing and conflict in our country, people are being asked to live by the agreements we have made.
It must be generously acknowledged that Mr McGuinness, the politician, travelled that road without equivocation.
As education minister in the first power-sharing administration in the late 1990s he set out a political method that would mark out his approach. He made a point of visiting schools from both traditions, helping dispel any pre-conceived perceptions of him among the unionist community. In challenging their notions of him and his past, he became an agent of change himself within his own political fold.
I recall, in particular, his unequivocal condemnation of dissident violence being an important stabilising influence and confidence-building measure of powerful symbolism and significance.
His attendance at a banquet given by the Queen in Windsor Castle during the state visit of President Michael D Higgins was another significant moment.
I am sure he was disappointed that resigning from office proved to be the only option he felt open to him, if political relationships within the Executive and the Assembly were to be re-set on a proper course consistent with the principles of equality and mutual respect. His skills will be missed now in that effort.
A successful re-establishment of the power-sharing Executive on a sustainable basis, with a working method of mutual generosity and respect, would serve as a poignant memorial to him.
On a personal note, I am very sorry for all his family and friends for his untimely death.