About a year-and-a-half before Martin McGuinness died, a leading member of the DUP explained his importance to the peace process generally and the DUP/Sinn Fein relationship in particular: “Martin looks upon (Nelson) Mandela as a role model. He is serious about reaching out to unionism and trying to understand the problems we face. He was serious about working with (Ian) Paisley. He is serious about working with Peter (Robinson). He obviously wants a united Ireland, but I think he’s probably willing to let it wait until the circumstances are right for all sides. The relationship hasn’t been perfect and has required a lot of behind-the-scenes hard work from both him and Peter; but I’ll tell you this, we couldn’t have got this far without McGuinness fronting for Sinn Fein. Once he goes, unionism will have a problem.”

That conversation took place on September 14, 2015, a few days after Arlene Foster – standing in for Peter Robinson as First Minister – had said in an interview with BBC Northern Ireland’s Mark Carruthers: “I have been placed there as a gatekeeper to make sure that Sinn Fein and SDLP ministers don’t take actions that will damage Northern Ireland and principally, let’s be honest, that damage the unionist community. If anybody knows me… they know that I’m not going to put at risk to the people of Northern Ireland the possibility that rogue Sinn Fein or renegade SDLP ministers are going to take decisions that will harm the community in Northern Ireland.”

That interview angered Sinn Fein, particularly at grassroots level. It also angered McGuinness. Rumours were already flying that Robinson would be standing down as DUP leader and First Minister (he was gone from both roles four months later) and the odds seemed to favour Foster as his successor, although Nigel Dodds was also a contender. Who the DUP chose mattered, primarily, because of the importance of sustaining a good working relationship with McGuinness.

One sensed from the outset that the McGuinness/Foster relationship was a difficult one. Within a matter of months there was an Assembly election – a very strong performance from the DUP – followed by the formation of an Executive in which, for the first time, the DUP and Sinn Fein (with the exception of Justice) found themselves locked together.

They brought in a new director of communications to ensure that internal and external difficulties were monitored and contained and, on November 21, 2016, issued a joint article in which they claimed that their joint relationship was strong and that they were bound together on delivering good government for Northern Ireland.

Yet, within days, it was clear that Sinn Fein’s grassroots were not happy with what looked like an “overly comfortable” relationship with Foster. They didn’t like her. In fairness, deep down they didn’t like Robinson all that much either, but they did have a grudging respect for him. It was also true that McGuinness and Robinson had a respect for each other. But it was different with Foster.

Yet, even when the RHI story broke in early December, McGuinness was still prepared to offer Foster the lifeline of standing aside for a few weeks. Her refusal to take it was to be the final straw.

His illness played a part in what followed – resignation was the only option available – yet illness alone doesn’t fully explain the sheer anger and frustration of his resignation letter. In essence, he felled the Assembly and Executive. He blew apart the fiction of a comfortable relationship between himself and Foster. He finally admitted what some of us had been saying for years, namely that there were huge, unresolved internal tensions between both parties.

Crucially, he was saying that he had gone as far as he could go with the DUP. And, in saying that, he left the door open for his successor to set out the “no return to the status quo” mantra. Because, as we now know, the status quo seems to have involved McGuinness being instrumental in keeping Sinn Fein in the process even though – while he was able to work with Paisley and Robinson – the party grassroots and inner circles harboured grave doubts about the DUP’s overall commitment to working with it.

Some people in the DUP – and other sections of unionism – have told me that they think that a “sick, dying McGuinness” was manipulated into writing a ferocious letter by Gerry Adams, the argument being that Adams believed unionism had been weakened and republicanism strengthened by the fallout from Brexit.

They think he wanted to force an election, because they also think that he sensed that Foster had damaged herself over RHI, that her unpopularity across nationalism would help Sinn Fein (and this was before the “crocodile” comment) and that a wave of sympathy for the very ill McGuinness would also galvanise Sinn Fein’s support.

I’m not entirely persuaded by that argument. But I do think that the respect in which republicans – even those who didn’t normally vote for Sinn Fein – held McGuinness was such that the palpable anger of his resignation letter made them rally to the party.

Yes, the “crocodile” stuff was an electoral bonus, but the sense I had at the time – during the March 2017 Assembly election – was that this, as one Sinn Fein MLA put it to me, was: “All about Martin. All about a man who had done his best to reach out to unionism and shore up the peace process.”

McGuinness’s absence has left a huge hole in local politics. There is no one – and I really do mean no one – within Sinn Fein’s ranks with the clout he had. Whatever unionists may think of McGuinness – and many of them hated and still hate him – he did have an insight into what made unionists tick.

He talked, he read and he listened. He made a point of quiet conversations with people within the unionist community. It would be nonsense to claim that he had any sympathy for unionism or for unionists as a political class. That said, I think he did understand that unionism was, unlike Sinn Fein, a diverse, complicated entity that remained on a difficult journey.

Yet, when all is said and done, his final political act was to bring down the Assembly and Executive. More than that, he also chose to put the full weight of his boot into the DUP, holding it personally responsible for creating obstacles and hindering progress.

And therein lies the ultimate irony. The man who did so much to prop up the institutions and take the DUP on trust was the man who brought them down and left a new chasm between both parties.

The DUP source I quoted at the start was right. McGuinness is gone. And unionism has a problem.

Belfast Telegraph