RHI: The scandal that pulled down Stormont
The Renewable Heat Incentive, first launched in Britain in November 2011, was designed to meet targets for renewable energy consumption and reduce reliance on fossil fuels.
Six years on and the full story of its disastrous implementation in Northern Ireland is still emerging, with the aftershocks likely to be felt long after a public inquiry has reached its conclusions.
How did a government project designed to encourage responsible fuel consumption end up encouraging the exact opposite?
As the only devolved institution in the UK to have full control over energy, Stormont's decision not to have a cap on costs built into the non-domestic scheme was the initial cause of the cash-for-ash scandal.
The warning signs were there early on, first through a consultation in 2011 in which 13 respondents expressed concern over possible 'over-incentivisation'.
Following the introduction of the scheme in November 2012 in a department run by a woman who would later go on to be First Minister, RHI operated with a low-take up and without incident for the first 10 months.
That was until September 2013, when Arlene Foster was contacted by a whistleblower who raised concerns "not taken sufficiently seriously" at the time.
The same whistleblower would come back again through email in April 2014 detailing how RHI was being abused and would later describe how her concerns were "swept under the carpet”.
While it may be excusable to ignore a solitary whistleblower in a busy government department, where RHI was not a policy priority, a lack of action when abuse is suspected is another matter.
Arlene Foster may have known of concerns about the lucrative RHI tariffs as early as July 2013 through a second government consultation document into the scheme, while a minute from a department meeting on October 21 2015 states the implementation of cost controls were delayed under Mrs Foster's instruction.
"It was a ministerial decision to look at the domestic scheme rather than pushing through the trigger points on non-domestic which would have significantly delayed the implementation of the domestic scheme” an unidentified DETI official said.
The claims, strenuously denied, are at the centre of the political catastrophe faced by Mrs Foster, with her for reputation for responsibility and prudence perhaps lost forever.
Ministerial responsibility places the former First Minister firmly in the cross-hairs of the upcoming public inquiry and while Mrs Foster repeatedly states she did nothing wrong, she will be judged on her lack of action to stop or amend a scheme which could cost the Northern Ireland taxpayer £500 million
In April 2015 another potential opportunity to implement cost control measures and limit the government spend was missed.
Two-and-a-half years on from its introduction, DETI was due to seek re-approval for RHI from the Department of Finance and Personnel, but due to "administrative oversight" and changes in staff this did not happen.
The Northern Ireland Audit Report would later reveal DETI only realised their error a full month later.
If RHI was not a priority for government in its first two years of operation, in the autumn of 2015 it came to the fore.
From September to November there was a critical spike in people seeking into the scheme, with the total of 984 applications in that period almost as many as in the previous 34 months.
To put this into perspective, an underspend of £15m was reported by the department in the previous financial year.
This spike is to date unexplained, but it is suggested applicants were being urged by various sources to avail of a scheme 'too good to be true', before common sense prevailed and costs were capped.
Then DETI minister Jonathan Bell says he wanted to alter the tariffs on October 1 2015 but interference from DUP special advisers delayed this until November 17 - claims denied by those involved.
Correspondence has also emerged from the Ulster Farmers Union calling for the tariffs to remain open until January 1, 2016.
The email sent by Tom Forgrave, a member of the UFU's poultry committee, was then followed up by another from senior policy officer, Christopher Osborne, who called for a "grace period".
Before the scheme was finally closed to new applications on February 29, 2016 there was still time for a second whistleblower to contact Mrs Foster identifying how a farm shed and factories with large boilers were running heat 24 hours a day just to make money, but by that time the damage to the public purse had been done.
The subsequent audit report from July last year concluded there was “serious systematic weaknesses from the start” and noted how spending was “potentially vulnerable to abuse”, but it does not answer key questions regarding the £490m overspend.
Since the scandal came to prominence Mrs Foster first resisted calls to step aside to facilitate an RHI inquiry, before the decision was made for her after the resignation of deputy First Minister Martin McGuinness on January 9.
The Department for Economy has pledged to bring the overspend down to zero, but has been hit by legal action taken by claimants to the renewable energy scheme, who on February 8 were granted leave to seek a judicial review of plans to cut tariffs.
On the same date the Attorney General said he is considering considering challenging the entire legality of the scheme because it was introduced without going before the full executive.
Then there's the small matter of an Assembly election on March 2 and a growing divide between Northern Ireland's two main political parties - the DUP and Sinn Féin.
We are told a public inquiry into RHI will begin after the election and be chaired by retired appeal court judge Sir Patrick Coghlin, but what form this takes and how long before it reports remains unclear.
What is evidently clear is there is no quick fix to a scandal that has already brought down a government and has the potential to burden public finances for years to come.