Asked recently to pick just one great memory from my time with Tony Blair in Downing Street, I went for the coming together of the Good Friday agreement that laid the foundations for peace in Northern Ireland. It was magical. A lot of that was about the collection of personalities from across politics that came together to make history – and Martin McGuinness was a big part of the success it became.

Those early talks with Sinn Féin after Labour came to power in 1997 were a risk for both sides. It was a risk for Labour politically, but it was in many ways a bigger risk for Martin McGuinness and Gerry Adams.

At various moments during the years of negotiations that followed, Sinn Féin would frequently be exasperating, and some of us would lose our patience. Tony once suggested we should be a little more sympathetic to their difficulties, pointing out that they were going about this business with a not unreasonable fear that someone might put a bullet in their heads even for talking to us.

Whenever there is a terrorist attack politicians and media will rise as one to call it “a cowardly act”. But that means we should acknowledge the flipside too: what Martin McGuinness and the Sinn Féin leadership did in negotiating for peace took courage. Once he decided to make the change to pursuing democracy – and I believe he did so some years before New Labour came on the scene – I think he genuinely made the change. As time went on I saw somebody very different from the murderous hardman IRA commander image. I saw someone who was very human, very likeable, and dedicated to making the new path he had chosen work for the people he represented.

I grew to like him a lot on a personal level. Of course I am aware of what he did, and what the IRA were responsible for, but in a sense that makes it even more impressive he became the political figure that he did.

The run-up to the Good Friday agreement involved a configuration of such different personalities across the board – but somehow it worked. And McGuinness made an interesting double act with Gerry Adams. In their different ways, they both brought something very special to the process that wasn’t just about their movement reaching that point in its history. It was about them as leaders, and as men.

Adams would often talk in grand terms, and then McGuinness would come in with an absolutely chiselling point about what they wanted right there, right then and why they needed it right there, right then. They were difficult to deal with, because of the complexities and because of what was at stake, but also somehow very straightforward.

You could have a really straight conversation with McGuinness. Also, I know that the idea of having a laugh with Adams and McGuinness to some people would be terrible – but they did have a sense of humour.

I remember the first time the two of them came to Downing Street, there was a messenger in Downing Street, called Vera Doyle, who was Irish. She came over at one point and she said to McGuinness of TB: “Listen, you just be kind to my boy now, you just be good to him and make sure this thing goes well.”

And he just said: “Ah, don’t you worry, we’ll help him out.”

It was not difficult to develop a rapport with him. He was a big football fan, especially Manchester United, and every time we met he would always know how my team, Burnley, was getting on. And I remember around Christmas time in 2014, we had a “beautiful scenery tweet-off”. I was in the Scottish Highlands and he was in Northern Ireland and we were tweeting pictures of wonderful scenery and asking our followers which was better.

I last spoke to hima few weeks ago. I have recently been working on a novel about football in the 1970s and one of the plotlines relates to the IRA bombing campaign on the mainland.

I picked his brains about that, and we had a chat about Brexit. Unlike me, he has had the advantage of a meeting with Mrs May about it. He was on the rampage about Brexit. He feared there was a lack of understanding about the potential unintended consequences for the peace process. In particular he was shocked at the lack of thinking about how we could leave the single market and the Customs Union without a hard border and the risks that posed to the process. He worried about leaving Europe and he worried about the way British politics was going. He said he was worried Britain was turning into a one-party state.

Of course I did see him change over the years. We all have impressions of people before we meet them. In the early days, in the formal meetings he came across as tough-minded, abrupt. But as time went on, he became much more understanding of other people’s positions – and that was important when he took a senior position in the Northern Ireland executive.

After the Good Friday agreement, when he was getting on with the business of government in Stormont I pointed out to him: “You used to spend all your time hanging out with Kofi Annan and Bill Clinton, and now you’re spending your time worrying about how many colouring books to get into primary schools.”

But he loved that work on education. He got to direct policies that would affect children all across Northern Ireland. In some ways it is sad that the last chapter of his political life was the breakdown of the power-sharing executive in Northern Ireland that triggered the most recent election.

Tony Blair always said that peace processes never stand still: they either move forwards or they move backwards. Martin McGuinness was someone who, once he made the choice of democracy over terror, wanted to move the process forward. I’ll always remember landing in Belfast and seeing a huge poster with him and Ian Paisley laughing side by side with the tagline: the chuckle brothers. And it struck me how far he had come, and the courage that it must have taken to get there. Of course his terrorist past is a big part of his story. But so is the choice he made to leave it behind, which led to his enormous contribution to one of the most significant changes of our lifetime; one he feared was being taken for granted amid all the other changes going on.