On 22 January 2016, enterprise minister Jonathan Bell signed off on his approval to close the RHI scheme but that was rescinded about 20 minutes later.

It emerged from Mr Bell's adviser Tim Cairns a few days later that the decision was "in the hands of DUP party officers".

David Scoffield, the inquiry QC, says it appears to have happened because Mr Cairns hadn't received clearance from senior DUP adviser Timothy Johnston.

Image source, Getty Images

Arlene Foster says the matter was "cross-cutting and controversial" and should've been referred to the first and deputy first ministers: "It wasn't just the DETI minister who had to be satisfied."

She tells the inquiry that some big decisions required clearance from Stormont's top two ministers and therefore needed to be agreed by both the DUP and Sinn Féin.

Remembering one submission on a tourism strategy, she says Sinn Féin "wouldn't sign it off" because it referred to Northern Ireland, and she adds: "It sat and it never got approved."

Northern Ireland's then most senior civil servant Sir Malcolm McKibbin said that Arlene Foster was "better not implicated" in the RHI debacle, according to a top DUP adviser.

The quote is recounted in an email from Richard Bullick to fellow DUP advisers at the end of January 2016.

It read: "[Sir Malcolm] seems very concerned about spending out of control. Says will be huge audit issue and AF better not implicated."

Image source, RHI Inquiry

Asked what she believes that meant, Mrs Foster is "not clear" - pressed for an answer, she says it could be that Sir Malcolm thought it was up to DETI to find a solution to the RHI disaster.

She says she was involved in RHI matters at that time because the need to get the scheme under control had been escalated to the first and deputy first ministers.

"How could I be distanced from it when I was in the office of first minister?"

Arlene Foster says the first time she had "a detailed understanding" of the RHI scheme's emerging financial crisis was when she spoke to the head of the civil service Sir Malcolm McKibbin (below) on 27 January 2016.

Image source, NI Assembly

Inquiry counsel David Scoffield QC says it appears that DUP advisers Timothy Johnston and Dr Andrew Crawford were aware of the problems before that.

Asked if they spoke her her about it, Mrs Foster says she can't remember.

Jayne McCormack
BBC News NI politics reporter

The DUP leader said it was a "great regret" that she did not sack Jonathan Bell as a Stormont minister in 2016.

Mr Bell succeeded Arlene Foster as enterprise minister and became responsible for the RHI scheme from May 2015.

Image source, PA

But some inquiry witnesses have claimed that he was not suitable for a ministerial role.

Mrs Foster told the inquiry that when she became DUP leader and first minister she held the same belief but was told by other officials within her party: "How much harm can he do in three months?"

Everyone's been fed and watered and has returned to the Senate chamber for the afternoon session.

Image source, RHI Inquiry

Just to set the scene for you, the inquiry is discussing matters that happened in January 2016 that led to the ultimate closure of the RHI scheme at the end of the next month.

If you want to watch the proceedings, just click play on the video at the top of this page.

The inquiry is on a break to allow everyone to refuel - no pun intended - so join us again from 14:05 for more from Arlene Foster.

Mrs Foster says she had never heard of the potential for fraud in the RHI scheme before she saw the letter from her constituent detailing his serious concerns about how the initiative was being run.

She says was "essentially acting as a postbox" for her constituent and that in passing to the head of the civil service she knew it would be "dealt with in the appropriate way".

Image source, Pacemaker

In his evidence to the inquiry, senior Sinn Féin figure Aidan McAteer claims that the letter "was not shared with" the then deputy first minister Martin McGuinness.

Mrs Foster challenges that view, saying that if she didn't give it to Mr McGuinness she spoke to him about it.

"I would've imagined that Sinn Féin were aware of that document," she adds, saying that anything she had access to as first minister could also be seen by Mr McGuinness.

In January 2016, Arlene Foster received a note from constituent George Gallagher listing concerns about how the RHI scheme had been "seriously abused by many".

He gave examples, including how large factories that had not previously had any heating had three biomass boilers installed with the intention of running them "24/7 all-year round" to collect £1.5m over 20 years.

Another example was a farmer "who has no business or need for biomass boilers" and who was aiming to collect £1m over 20 years by "heating an empty shed".

It was that letter that prompted an internal civil service investigation into the scheme.

Mrs Foster says she gave it to her adviser Timothy Johnston, who passed it to the head of the Northern Ireland Civil Service and it was subsequently given to DETI's internal auditors.

Jonathan Bell "hero-worshipped" Peter Robinson (below) and "never really accepted" Arlene Foster's leadership, says the DUP leader.

The relationship between her and Mr Bell "deteriorated" over his views on the RHI scheme in the winter of 2015-16 and "he retreated and basically wouldn't speak to anybody", she claims.

Image source, AFP

Mrs Foster says that he took Mr Robinson's advice at that time instead of dealing with "the person who had been appointed the leader by the party".

"He had a real difficulty when Peter left."

It is "a great regret of mine", says Arlene Foster, that she did not sack Jonathan Bell as a Stormont minister when she became Northern Ireland's first minister in January 2016.

She didn't feel that Mr Bell "acted in an appropriate way as a minister", he didn't take his the post "seriously enough" and he "saw it as a role where he was to be served rather than to serve".

It was her "belief that he wasn't a suitable candidate for the post" but she decided to keep him on until the 2016 assembly election a few months down the line because sacking him could've harmed his prospects of re-election as an MLA.

She adds: "The view was expressed to me: 'How much harm can he do in three months?'"

And she claims that it was put to her that he would go "rogue" if he was sacked as a minister.

In October 2015, DETI put a business case to the finance department, seeking retrospective approval of spending on the RHI scheme and approval of future spending.

Image source, RHI Inquiry

Arlene Foster says it wasn't brought to her.

She says it may be that the business case should've been brought to the Northern Ireland Executive "given that it was a cross-cutting issue and had a potential to become novel and contentious".

In November 2015, Arlene Foster asked whether an assembly debate on passing the RHI scheme's cost controls could be delayed by a week or two.

It came after a query from constituent Stephen Harron, who was working for a boiler installation firm.

Mrs Foster put the query to Tim Cairns, the DETI ministerial adviser, who passed it to officials in the department.

Image source, PA

Dr Andrew McCormick, the most senior civil servant at DETI at the time, told the inquiry that Mr Cairns referred to a concern that "not enough businesses in Fermanagh had been able to apply" before the cost curbs would take effect.

Asked about that, Mrs Foster denies that was mentioned in her request and she says that "when people see Foster they see Fermanagh" but it "wasn't the case on this occasion".

Officials worked out that delaying the cost controls by just a week would've added at least £2.6m a year to the cost of the initiative over its 20-year lifetime - Mrs Foster says that when she heard about that cost "that was the end of it".

On the subject of ministerial responsibility and accountability for the action of advisers, Arlene Foster says there was no training for newly-appointed ministers.

Image source, RHI Inquiry

"You are literally thrown in at the deep end and there's no 'let's have a training day' to give you some indication as to what your responsibilities are as a minister," she says.

That's a shortcoming, she says, that she hopes can be rectified when the Northern Ireland Assembly "gets up and going again".

Arlene Foster says that she can't see how she is responsible for the actions of her adviser in sharing confidential papers about the impending cost controls for the RHI scheme with two family members.

Dr Andrew Crawford released the sensitive information in the summer of 2015 before it had been signed off by a minister.

Image source, Getty Images

Given that he was meant to be acting on her behalf, Mrs Foster is asked what responsibility she bears for what he did.

"If an individual acts outside what they should be doing... then they've stepped outside of the rules and have broken those rules," she says.

"I'm accountable for that breach but I fail to see how I could be responsible for that breach."

In his written evidence to the inquiry, Timothy Johnston - who advised the first minister - says he had "no sense that there was... a recognised hierarchy of advisers" within the DUP.

But Tim Cairns - Jonathan Bell's adviser - took a different view, telling the inquiry that everyone within the party knew that Mr Johnston was "at the top of the tree".

He claimed that he was told by Mr Johnston to talk to Arlene Foster's adviser Dr Andrew Crawford about the RHI scheme and he also said that Mr Johnston told him that cost controls would not be introduced.

Mr Johnston denies that he had any role in delaying the cost controls for the scheme.

Mrs Foster's view is that advisers to the first minister shouldn't interfere with the work in another department because they wouldn't be across the relevant detail.

The inquiry has heard from some witnesses that there was a "hierarchy" of ministerial advisers within the DUP.

Arlene Foster says in her written statement that if an adviser to the first minister expresses a view "it is likely to be considered to be the view of the first minister".

Image source, RHI Inquiry

She goes on to say that she doesn't believe there was "a hierarchy of advisers, per se".

Asked to explain that, she says that all three of the first minister's advisers "would have had, on occasions, to speak to other advisers about the first minister's view".

"Therefore they do have a seniority because they are the first minister's special adviser."

Emerging budget concerns about the RHI scheme were not brought to Arlene Foster by her finance department officials in the summer of 2015, in spite of numerous contacts between the department and DETI on the matter.

Mrs Foster says she was not aware of what her officials knew at the time and having read through the evidence it's still not clear to her what they knew.

She says: "If they had come forward and said: 'DETI have an issue with [irregular spending] and they don't know how much budget they have', then I would have said: 'Well, we need to find out - we need to get clarity in relation to this issue.'"

Arlene Foster accepts that the inquiry has major questions about what her DUP adviser Dr Andrew Crawford was doing in relation to the RHI scheme.

Dr Keith MacLean, the inquiry's energy expert, says that the adviser had been giving "bad advice" in relation to the RHI scheme in July 2015.

Image source, RHI Inquiry

Dr Crawford had suggested a change to the cost controls that were being planned at the time.

His proposal - which was immediately rejected by civil servants because it offered no value for money - would've effectively meant that claimants would continue to receive big subsidies even after the cost controls came into effect.

Dr MacLean tells Mrs Foster: "It gives us a big question as to what on earth was your [adviser] doing in this involvement without your knowledge."

In July 2015, Arlene Foster's adviser Dr Andrew Crawford (below) emailed Tim Cairns - his successor as the DUP adviser at DETI - to say that the "problem" with the RHI scheme was that it "pays producers to heat houses when... [they] are empty".

That "logically seems to suggest" that Dr Crawford was aware that there was an incentive to simply burn fuel to earn money, says Mr Scoffield.

Mrs Foster says her adviser didn't tell her about that but he should've done so.

Sir Patrick Coghlin says that's an example of why "one would get so concerned" about the DUP's selections of advisers, pointing out that Dr Crawford had knowledge of what was happening with the scheme and was making suggestions in relation to it.

"All of this was being done by an unelected [adviser] and about which you as the minister have no knowledge", he tells Mrs Foster.

Dr Keith MacLean asks about the existence of an "inner circle" of advisers with the DUP "where tenure is not going to be an issue".

Arlene Foster says she doesn't think that was the case as the advisers loses his or her job if the minister they are working under minister loses theirs.

Image source, RHI Inquiry

Sir Patrick Coghlin says the inquiry has heard that phrase: "Ministers may come and ministers may go but [advisers] go on for ever."

Mrs Foster laughs, saying she's "not sure that that's the case".