We've come to abrupt halt as inquiry barrister Joseph Aiken's famous railway metaphors hit the buffers.

"This train has finally reached its destination and is being parked up for Christmas," he says.

Inquiry chair Sir Patrick Coghlin thanks him profusely for "the degree of work and detail that you have put into it".

The speed of today's presentations has taken the panel by surprise so they have time to nip off and get some last-minute Christmas cards written.

Join us again tomorrow at 09:45 for what we promise will be the final public session of the RHI Inquiry.

Inquiry counsel Joseph Aiken takes the panel back to an intriguing period in March when an official from the RHI scheme's administrator said that DUP MP Ian Paisley had lobbied her to accept an application for a more lucrative subsidy as rates were being cut.

That official was Ofgem's Teri Clifton - she said Mr Paisley had been one of several people involved in a "very intimidating" phone call on behalf on an applicant to the scheme.

A few days after she gave her evidence she was attacked in the House of Commons by Mr Paisley (below), who described her allegation as a "calumny" and called for her to be brought back to the inquiry and "put through the wringer" to explain it.

Mr Aiken explains what has emerged since all of that happened - evidence has been received by the various individuals involved in the conference call.

Firstly, Ofgem told the inquiry that Ms Clifton "found what had been said about her in Parliament deeply upsetting".

She has since said she was told during the call that Mr Paisley was present and she stands by her account.

The applicants involved in the call - Sean and Anne McNaughton - have said in a witness statement to the inquiry that Mr Paisley was not involved and nor do they remember any reference to Mr Paisley being made.

The McNaughtons also said they were not intending to intimidate anyone during the call.

Another participant in the call backs up the McNaughtons' view that Mr Paisley was not involved.

Mr Aiken tells the inquiry panel that it may consider Mr Paisley's public accusation against Ms Clifton that she had lied to have been "unjustified in the circumstances".

He also says the panel may take the view that the McNaughtons "feel very aggrieved about the entire situation".

Jonathan Bell's decision to go public with his allegations about DUP advisers' role in the RHI scheme was "motivated by two factors", says Ronan Lavery.

Firstly, he wanted to reduce the vast overspend on the scheme and the money to be returned to the public purse.

Image source, Getty Images

He also wanted to make sure that the "misgovernance was something which would not happen again".

"His commitment has been to act justly.... the only thing guiding him was the public interest."

"Many of the headlines" in the RHI fiasco have been personal about Jonathan Bell, says his barrister.

A "personal animosity" is "something that he has had to face in the media", adds Ronan Lavery (below).

One allegation that he had tried to break the finger of his adviser Timothy Cairns during a row in a London hotel "turned out to be completely untrue".

Image source, RHI Inquiry

There was a desire to blame Mr Bell for the RHI disaster and for the delay in adding cost controls to the scheme and ultimately shut it down, adds Mr Lavery.

"That criticism... has only ever come from two quarters - from the DUP and from [ministerial advisers] - and nobody else has sought to blame Mr Bell for any delay in the scheme," he says.

The barrister says Mr Bell did everything he possibly could to close the scheme.

The RHI Inquiry "probably would not have been held" if former DUP minister Jonathan Bell hadn't revealed the details of the scandal in his interview with the BBC's Stephen Nolan in December 2016, claims his barrister.

Ronan Lavery QC says Mr Bell has been the "subject of personal attacks and smears" - those include accusations of "violence, drunkenness, incompetence" - since he did that in an attempt to "undermine the truth of what he is saying".

Image source, Pacemaker

His actions have come at "enormous personal and professional expense".

Mr Lavery sets out Mr Bell's career, saying he has a "distinguished" academic and political background.

Mr Bell was a social worker before entering the political world and since he lost his seat in the Northern Ireland Assembly last year he has returned to that career, says the QC.

On the subject of whether or not he was instructed by top DUP adviser Timothy Johnston to liaise with Dr Andrew Crawford on RHI, Timothy Cairns has told the inquiry that the course of action was agreed to at a meeting where his minister Jonathan Bell was present and he did not object.

His barrister Richard Smyth says it must be borne in mind that it was part of the adviser's role to "act as a communication panel between the party and the administration".

Image source, RHI Inquiry

Therefore, he says, the course of action adopted by Mr Cairns was an entirely reasonable one.

Turning to the critical meeting of 24 August 2015 when the decision was taken to put back the RHI scheme's cost controls to 4 November that year, Mr Smyth says the date was effectively in the hands of officials.

The lawyer claims that the primary cause for the delay "was the time taken to draft and clear regulations".

Next up to deliver closing remarks is Richard Smyth, the barrister representing former DUP adviser Timothy Cairns (below).

Mr Cairns was the ministerial adviser from May 2015 to Jonathan Bell, the DUP's enterprise minister at the time.

A written closing submission has been submitted to the inquiry on his behalf - you can find it here, external.

Image source, RHI Inquiry

His legal representative says his main point is that Mr Cairns "acted reasonably and appropriately and did not breach relevant codes pertaining to his role" in relation to the work on introducing cost controls to the RHI scheme in 2015 and the closure of the initiative in early-2016.

Mr Smyth admits that's not to say things could not have been done better.

He explains that a row in London between Mr Cairns and his minister in June 2015 did not have a direct effect on a vital ministerial paper about the RHI scheme's cost controls that summer.

Mistakes were made "at virtually every stage" of the RHI scheme, concludes the DUP's barrister.

"There were also mistakes made later in the heat of the political crisis in 2016 and early 2017," adds Julie Ellison.

She says that where those mistakes were made by the DUP, the party hopes the inquiry sees that they have been "accepted fully and freely, even where it has been difficult and painful to do so".

The inquiry has "understandably become interested in what is often perceived as the shadowy world" of ministerial advisers, says Julie Ellison.

In the cash-for-ash debacle, DUP advisers have "very much been the story," adds the party's barrister.

One of the big issues that got under inquiry chair Sir Patrick Coghlin's skin was that it was clear that rules around the proper appointment of advisers were bent or broken at Stormont.

Image source, Getty Images

Ms Ellison tells the inquiry that "at times the mandatory code has been honoured more in the breach than the observance" but "not in all cases".

She accepts that the rules "should have been adhered to more closely" but they should be "reconsidered so that there is more transparency and accountability surrounding the role".

It is "hoped that reconsideration" of some aspects of the rules surrounding advisers will allow them to "stay out of the spotlight - that is, out of the shadows but no longer shadowy".

Stormont ministers "are reliant on their officials to bring relevant issues and information to their attention accurately", says the DUP's barrister.

Ministers and advisers don't have access to the advice offered to previous ministers.

Image source, RHI Inquiry

"This makes it difficult if not impossible for ministers to independently root around in policy issues," says Julie Ellison.

She adds that ministers cannot be across the detail of every policy on which 500 departmental officials are working.

One of Arlene Foster's points in her evidence was the her officials when she was enterprise minister didn't do enough to draw major issues with the RHI scheme to her attention.

A woman who tried to alert Arlene Foster to the fundamental flaw in the RHI scheme is "deserving of an apology" for her treatment by the DUP when it was trying to protect its leader at the height of the RHI storm in December 2016, says Julie Ellison.

Janette O'Hagan, who's been referred to as a whistleblower, sent emails about the scheme to Mrs Foster in August and September 2013 and the then minister referred the correspondence to her officials.

Image source, RHI Inquiry

During her time before the inquiry in February, she was highly critical of how the party had treated her, saying it was a "complete disgrace" that it had published her correspondence on Twitter.

It had been poorly redacted, she said, meaning that people could work out her identity.

Referring to Mrs Foster's actions when she received the emails from Ms O'Hagan in August and September 2013, Ms Ellison says that "given the volume of correspondence received by the minister... it would be unrealistic for Mrs Foster to have specifically followed up" on it.

Barrister Julie Ellison turns to allegations against DUP advisers that she says "have perhaps been the subject of the most intense scrutiny, particularly within the public and the media".

Former enterprise minister Jonathan Bell (below) claimed that in summer 2015 DUP advisers sought to delay the introduction of cuts to subsidies on offer from the RHI scheme that were designed prevent its costs running out of control.

Image source, RHI Inquiry

In particular, it was claimed that senior DUP adviser Timothy Johnston (above) had directed Mr Bell's adviser Timothy Cairns that subsidy cuts would not be introduced and that he should engage with fellow DUP adviser Dr Andrew Crawford in working on the scheme.

Ms Ellison says it was the clear evidence of Mr Johnston - now the DUP's chief executive - "that he had neither knowledge of nor interest in the Renewable Heat Incentive in June 2015 such that he could have made any such comment or direction".

Arlene Foster's (below) barrister says there was a "number of key points" at which information about the RHI scheme that was given to the then enterprise minister "was not presented in a clear or straightforward manner".

Image source, Reuters

Julie Ellison says Mrs Foster was advised in 2008 and 2009 that there was "no evidence" that joining the Great Britain RHI scheme would "be the best course for Northern Ireland".

"With the benefit of hindsight, we can look back ruefully at that decision and reflect on how differently all this may have turned had we joined... the GB scheme."

It has been "difficult and painful at times" for the DUP to have its dealings laid bare at the RHI Inquiry, says Julie Ellison (below), the barrister representing the party.

The role of the DUP in the cash-for-ash debacle "has been the subject of much media and public interest, speculation and criticism" from the moment the "very aptly-named BBC Spotlight programme shone a public spotlight" on the botched RHI scheme in December 2016, she adds.

But the DUP has "welcomed the inquiry as a means of establishing the truth".

Image source, RHI Inquiry

It hopes that the inquiry's findings will lead to "lessons to be learned at every level of government" and the DUP "is certainly committed to learning those lessons".

Ms Ellison is speaking for DUP members who've been given enhanced participatory rights in the inquiry due to their position or involvement in the RHI scheme.

They are party leader and former enterprise minister Arlene Foster and former advisers Stephen Brimstone, Dr Andrew Crawford, Timothy Johnston and John Robinson.

They have all submitted closing statements in writing, which you can find on the inquiry's website, external.

Conor Macauley
BBC News NI agriculture correspondent

A senior lawyer in the organisation that was administering the RHI scheme advised a colleague not to share some information with police who were investigating a DUP adviser for fraud, the inquiry was told.

Ofgem's John Jackson told a colleague that under data protection laws she should not give the PSNI an audit report on an RHI-registered boiler belonging to Stephen Brimstone (below), who was an aide to DUP leader Arlene Foster.

Image source, RHI Inquiry

His advice came after an anonymous allegation led the police to open an investigation into Mr Brimstone, who had fitted the boiler in a shed at his house but it was mostly used to heat his home.

Mr Brimstone's application suggested that heat was also provided to the shed, which was sometimes used agricultural purposes.

The Ofgem audit found little or no evidence to substantiate that claim but after further information supplied by Mr Brimstone it ruled that his installation was compliant with scheme rules.

BBC News NI

An independent inquiry into the RHI scandal was established in January last year by the then finance minister Máirtín Ó Muilleoir.

He ordered it in the wake of the huge public concern at what was then a major political crisis surrounding the scheme.

The RHI Inquiry began in November last year and Sir Patrick Coghlin (below), a retired Court of Appeal judge, is its chair and has been given full control over how it operates.

Image source, Pacemaker

It is looking at:

• the design and introduction of the RHI scheme
• the scheme's initial operation, administration, promotion and supervision
• the introduction of revised subsidies and a usage cap for new scheme claimants in autumn 2015
• the scheme's closure in February 2016

For more information on the RHI Inquiry, you can read our handy Q&A.

When the scale of the overspend emerged, public and political concern rocketed.

As the minister in charge of the Stormont department that set up the RHI scheme, the Democratic Unionist Party (DUP) leader Arlene Foster faced calls to resign from her role as Northern Ireland's first minister in December 2016.

Image source, Pacemaker

She resisted and Sinn Féin's Martin McGuinness then quit as deputy first minister in protest at the DUP's handling of what had by then become a full-blown political crisis.

That move brought about the collapse of the Northern Ireland Executive. Now, almost two years on from that, Northern Ireland remains without a devolved administration.

You can find much more detail on the RHI scheme in our need-to-know guide.

The budget of the RHI scheme ran out of control because of critical flaws in the way the initiative was set up.

Claimants could effectively earn more money the more fuel they burned because the subsidies on offer for renewable fuels were far greater than the cost of the fuels themselves.

At one point the estimate for the overspend was set at £700m if permanent cost controls weren't introduced - temporary cuts have since pulled the budget back on track for now.

Whatever the scale of the bill, it will have to be picked up by the Northern Ireland taxpayer.

The Renewable Heat Incentive scheme - or RHI for short - came to the fore of the Northern Ireland public's knowledge in late-2016.

The fallout from the scandal attached to it is still being felt in the region's politics today.

Image source, Getty Images

The scheme was set up by the Northern Ireland Executive in 2012 as a way of encouraging people to switch from using fossil fuels to renewable sources for generating their heat.

Those who signed up were offered financial incentives to buy new heating systems and the fuel to run them.

Welcome to the hill at Stormont.

It's blowing fit to skin a fairy out there so come into the warm and grab a seat for the second day of these pre-Christmas wrapping-up sessions.

Today we'll be hearing from lawyers representing the DUP and some of its former ministerial advisers.

It promises to be an interesting session so stay with us for the live video stream and text commentary.