Gareth Gordon
BBC News NI Political Correspondent

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Julian O'Neill
BBC News NI Business Correspondent

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Mark Simpson
BBC News NI

Within moments of Speaker Robin Newton starting proceedings in the chamber, he suspends it for half-an-hour.

MLAs from Sinn Féin, the SDLP, the Ulster Unionists and the Green Party all walked out as the speaker refused to take points of order.

First Minister Arlene Foster was due to give a statement to MLAs on her role in the RHI scandal, but it was only provided to members 15 minutes before the sitting began.

Therefore, the sitting has been suspended until 11:00 to give members a chance to run their eyes over it.

Jayne McCormack
BBC News NI

December has seen the RHI scandal sweep along at a rapid pace.

Last week, former enterprise minister Jonathan Bell (above) made sensational allegations in an interview with the BBC's Stephen Nolan regarding the role of Mrs Foster and top DUP advisers.

He said the aides "intervened" to prevent the closure of the scheme at a crucial time, and had it been shut down when he had asked for, the extra £400m cost to taxpayers could have been avoided.

He also alleged that they tried to "cleanse the record" of references to Arlene Foster (below) and her department.

The advisers denied the claims and Mrs Foster also distanced herself from any wrongdoing.  

The first minister has faced calls for her resignation over her role in the project, and virtually every other party at Stormont called for a public inquiry into the matter.

On Friday night, Deputy First Minister Martin McGuinness said Mrs Foster should stand aside until an investigation was carried out.

But immediately, the DUP hit back, saying she would not be quitting, and adding that she "does not take her instructions from Sinn Féin, but from the electorate".

Mr Bell has since been suspended by the DUP.

So, just what is the Renewable Heat Incentive (RHI) scheme, and how has it led Stormont to yet another crisis point? Let's go right back to the start...

The RHI initiative was introduced in 2012 by the Department of Enterprise, Trade and Investment (Deti), then led by Arlene Foster, with the aim of increasing the uptake of renewable heat technologies.

But in July this year, the Northern Ireland Audit Office stated in a report, external that "serious systematic failings" in the scheme are likely to cost the Northern Ireland budget "hundreds of millions of pounds".

Economy Minister Simon Hamilton described the finding as "deeply shocking".

Image source, Tchara

The Audit Office investigation was prompted when a whistleblower contacted the Northern Ireland Executive in January alleging that the scheme was being abused.

One of the claims was that a farmer was aiming to collect about £1m over 20 years from the scheme for heating an empty shed.

At an initial Public Accounts Committee (PAC) inquiry session, a senior civil servant apologised for the department's lack of oversight in the scheme and said that by the end of it, it will have cost the public purse a grand total of £1.18bn.

In November, officials from Ofgem E-Serve, the scheme's administrators, gave evidence to the committee.

They came in for heavy criticism from MLAs, with the SDLP's Daniel McCrossan saying the scandal was "one of the biggest" that politicians had encountered since devolution.

Also in November, David Sterling, the Deti permenant secretary at the time of the scheme's set-up, told the PAC he was not "ducking responsibility" for the colossal overspend.

It's a grey, gloomy day here at Stormont as MLAs have been summoned back up the hill to Parliament Buildings for an unexpected sitting to address the first major crisis of the new assembly mandate.

The fallout from the Renewable Heat Incentive scheme scandal has heaped pressure on First Minister Arlene Foster, and she is set to give a statement in the chamber at 10:30.

We'll have live text updates throughout what could be an extraordinary day in the assembly, and you can watch proceedings live on this page, too.