Sinn Fein's Martin McGuinness.

It is a calculated abandonment of Sinn Fein’s strategy under his leadership – and potentially the valedictory act on his political career.

On the latter point, Mr McGuinness’s gaunt appearance, audible physical weakness and refusal to state that he will even be a candidate in what is likely to be a March election will lead many people to draw their own conclusions.

Mr McGuinness never reached – nor even came close to – the goal for which he fought, first in the IRA and then as a Stormont minister, of a united Ireland.

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Yet Mr McGuinness’s rise from humble beginnings in Londonderry’s Catholic Bogside to de facto joint prime minister of Northern Ireland would in itself have been an astonishing personal success had his goal not been so much grander.

Once seen as an IRA hawk, he has morphed into Sinn Fein’s most accommodating senior figure since his assent to office as Stormont’s education minister in 1999.

And, since taking over as deputy First Minister with Ian Paisley in 2007, his overt strategy has been to accept all manner of perceived or actual slights by Sinn Fein’s coalition partners, the DUP, or crises for the sake of ‘the process’. In that time, the Stormont institutions were to him sacrosanct. No longer.

Yesterday’s dramatic departure from office gave the imprimatur of the dove Sinn Fein leadership’s to a strategy which now views the very presence of devolved government in Northern Ireland as a bargaining chip with the Government and with the DUP.

Although the straw which has broken this camel’s back has been the Renewable Heat Incentive (RHI) scandal, Sinn Fein has known about this issue within government for more than a year and has shown scant enthusiasm for even making life difficult for the DUP over it, let alone collapsing the Executive.

But over the last month, since the BBC’s Spotlight investigative programme brought to a mass audience the scale of what at best is a £500 million ineptitude, Sinn Fein’s restrained response has been under growing pressure from its traditional supporters.

In many cases, their existing private view that the DUP has been running rings round Sinn Fein in government has been compounded by their party’s apparent inability to hold its coalition partner to account – even when half a billion pounds of public money are at stake and hospitals are under winter pressure.

As Mr McGuinness’s health has suffered and the crisis has deepened, Gerry Adams, who now sounds a much more hawkish tone in relation to Stormont, has returned north of the border in recent weeks.

The Sinn Fein president now speaks of a list of ‘unresolved issues’ from Sinn Fein’s perspective which is close to double figures and includes such long-forgotten demands as a Bill of Rights and issues which Sinn Fein hasn’t mentioned for months, such as the Red Sky scandal.

Mr Adams now appears to envisage yet another round of ‘crisis talks’ in Belfast in attempt to extract further concessions from the DUP and the Government, which Sinn Fein can then sell to its supporters in order to justify its continued position in a power-sharing arrangement with a party whose policies are far more right wing and far more unionist than those of Sinn Fein.

The price of power is compromise, and, having compromised on its goal of a united Ireland, Sinn Fein is struggling to sell further concessions to its supporters.

There is a second profound consequence of Sinn Fein’s actions yesterday.

Mr McGuinness’s message yesterday could be crudely summed up as “the DUP are bigots” and he cited the party’s approach in areas as diverse as gay rights and the Irish language as evidence.

That is starkly at variance with what Mr McGuinness has been telling the public for more than a year since the (now seemingly inaptly named) Fresh Start Agreement – even though the DUP’s position on those issues has not changed.

Little more than a year ago, Mr McGuinness said: “Our political institutions are the best way forward. The First Minister and I are absolutely united on this.”

And since the election the DUP and Sinn Fein have been working together in unrivalled harmony, even joining forces in the Assembly to lampoon the SDLP and UUP.

Their excuse that it was the smaller parties who were responsible for past Executives’ failures was removed in May with the creation of an Official Opposition and the Executive’s determination to present a united front was evident in the hiring of the respected journalist David Gordon as spokesman for their joint message.

In an article which it is understood was drafted by Mr Gordon, the ministers said: “We made promises to voters that we will keep – taking on the heavy responsibilities that come with elected office, governing in their best interests, tackling head-on the tough decisions.”

Those “promises” have been shredded a matter of weeks later, as has another pledge in the same article that they would not be “filling the airwaves with endless squabbles, making the Assembly a by-word for division”.

That united front went on despite Sinn Fein having known the brutal scale of the RHI losses for more than a year. It continued into what is described as a cordial Executive meeting on December 14 – a week after the BBC Spotlight programme.

It therefore appears that Sinn Fein’s decision has been taken in haste in a belated attempt to placate a nationalist electorate which believes that Sinn Fein either has been too soft in government.