The inquiry has run an hour beyond its usual closing time in order to complete Timothy's Johnston's evidence.

Long aul' day for all involved so we're away home for a lie down and we suspect everyone who was in the Senate chamber has the same intention.

But we'll be back tomorrow morning when the RHI Inquiry hit its century of hearings!

The witness will be Dermot Nolan of the RHI scheme's administrator Ofgem.

Join us in the morning from 09:45 for all the excitement...

BBC News NI

An email supplied to the inquiry by an ex-DUP adviser appears to show someone in the party did not want cost controls introduced in the RHI scheme.

In the email, Tim Cairns told fellow DUP adviser Timothy Johnston that they needed to "catch up" about the initiative.

Image source, RHI Inquiry

He also said that if they wanted to "deviate" from how a similar scheme in Great Britain had been set up with cost controls they would need to secure a formal command from a minister.

But Mr Johnston, now the DUP's chief executive, denied that he had given an order that cost controls would not be added to the scheme.

In closing his evidence, Timothy Johnston suggests that there should be greater transparency about the work of ministerial advisers.

"One of the effective remedies might be leadership on all parties," Sir Patrick Coghlin tells him.

Image source, RHI Inquiry

"There appears to be such a lack of leadership right from the top down into the civil service," he adds.

Mr Johnston agrees, saying that's one of the greatest challenges the political parties face in any negotiations at Stormont if devolved government is to be restored.

"Thankfully that's a matter for you lot, not for me!" jokes the inquiry chair.

The "origin" of the two-week delay to the RHI scheme's closure in February 2016 "came from Sinn Féin", says Timothy Johnston.

He says it was specifically from the MLA Conor Murphy (below, left).

There'd been a "big backlash" when the shutdown had been prematurely announced by Jonathan Bell, says Mr Johnston, and that created pressure from Sinn Féin "to give a couple of weeks' grace".

Image source, PA

The DUP needed Sinn Féin's support to get the closure passed in the Northern Ireland Assembly and Mr Johnston says there was a "sense" that allowing the delay "was a price worth paying".

Mr Johnston says Arlene Foster and Mr Bell had a "very fraught meeting" at Stormont when they discussed the delay.

The inquiry's heard all about that - Mr Bell claims he argued "as passionately as I could" for it to be shut, while Mrs Foster says he just "didn't want to look foolish".

Jonathan Bell alleged that a DUP adviser had tried to "cleanse the record" of references to Arlene Foster in an official document about the RHI scheme.

His adviser Tim Cairns admitted to the inquiry that he removed a reference in a paper in February 2015.

The document stated that the decision to shut the scheme had been reached after Mr Bell had discussions with the first minister and the finance minister.

Image source, Getty Images

But the changed document stated that Mr Bell had made the decision without consultation with other ministers - that was not true.

Mr Cairns sent the changed paper to Timothy Johnston, saying that he'd removed the reference.

Inquiry barrister Donal Lunny says some evidence suggests that the removal was an attempt to distance Mrs Foster from the "potentially toxic" RHI scheme and "gave her the flexibility to deny" association with it.

Mr Johnston says that "doesn't accord with reality", claiming that other documents show her involvement.

In January and February 2016, frantic attempts were being made at DETI to shut down the RHI scheme and there was a keenness in the first minister's office to have a say on how it was handled.

According to one senior DUP adviser, Northern Ireland's then most senior civil servant said that Arlene Foster was "better not implicated" in the debacle.

The comment is attributed to Sir Malcolm McKibbin in an email from Richard Bullick to fellow DUP advisers at the end of January 2016.

Image source, Getty Images

Shortly after that, Sir Malcolm made it clear in an email that the problem lay with DETI and it would have to sort it out.

Asked if it was an attempt to distance Mrs Foster from the situation, Timothy Johnston says he doesn't think so, explaining that whatever decision DETI took would ultimately have to be approved by the first and deputy first ministers.

"Mrs Foster was going to be in the middle of that process," he adds.

Tim Cairns said that a complaint he'd made about Jonathan Bell's "temper" went down "like a fart in a spacesuit".

There'd been an attempt by Timothy Johnston to get the two men to sort out their differences but it hadn't gone well and Mr Cairns wasn't happy that Mr Bell hadn't apologised for his part in the row.

He sent a text to Emma Little Pengelly to say that he was "dreading" his return to work with the minister.

Image source, AFP

And he subsequently complained to Mr Johnston that the situation hadn't been dealt with properly - Mr Johnston's response prompted the "fart in a spacesuit" text.

The messages clearly show that the two men hadn't made up and Mr Johnston says that if he'd been aware of them it "would've put a very different complexion on the situation".

Inquiry chair Sir Patrick Coghlin says that Mr Johnston's "so-called mediation was a disaster".

Tim Cairns told DUP colleague Emma Little Pengelly (below) that if he got the chance he was "going to film [Jonathan Bell] drunk and talking shit and show it" to Timothy Johnston.

He made the remark in a text to Ms Little Pengelly, now a DUP MP but then a ministerial adviser in the party.

Mr Cairns texted to say that he would "report [Mr Bell's] every transgression to [Mr Johnston] who wants him out".

Inquiry barrister Donal Lunny says those messages show a "highly dysfunctional relationship" between DUP advisers and Mr Bell and a "total lack of trust and confidence" between them.

Mr Johnston says Mr Cairns "knew that I would take the issue seriously" and would raise it with the then party leader Peter Robinson.

Text messages the inquiry has obtained from DUP adviser Tim Cairns show that he told a colleague that Timothy Johnston had issued a warning to the then Stormont enterprise minister Jonathan Bell.

Mr Cairns was the adviser to Mr Bell and they'd had a major falling-out on a work trip to London in June 2015 - the inquiry's heard all about that - and he left that row thinking he was about to be sacked by the minister.

On his return to Belfast, Mr Cairns discussed it with Mr Johnston - in texts to his colleague Emma Little Pengelly recounting what had happened in that meeting, he wrote: "[Mr Johnston] told [Mr Bell] that we were appointed and would be sacked together."

Image source, Pacemaker

According to Mr Cairns, Mr Johnston warned the minister that he "would go against the party officers at his peril" if he was to try to sack his adviser.

Inquiry barrister Donal Lunny says that suggests that Mr Johnston was in a position of potential authority over Mr Bell.

Mr Johnston says he wouldn't have entered discussions about the party officers because that was a matter for the first minister.

Timothy Johnston says he wouldn't have allowed Dr Andrew Crawford to have any involvement in advising on the RHI scheme in the summer of 2015 if he'd know that some of his family were claimants on the initiative.

Between them, Dr Crawford's brother and two of his cousins have 11 biomass boilers registered on the scheme.

Image source, RHI Inquiry

And the inquiry has found that Dr Crawford shared confidential papers about the scheme with one of those cousins.

Mr Johnston says it "wouldn't have been appropriate" to allow Dr Crawford to work on the scheme because a "perception of a conflict of interest, at least, arises".

Timothy Johnston claims there was "no interest in the RHI scheme at the castle" in August 2015 because of an unfolding political crisis between the DUP and Sinn Féin that left Stormont "on life-support".

Stormont Castle (below) was where the first and deputy first ministers and their advisers had their offices.

Mr Johnston says he had "enough other things to be doing" because of the political crisis that was sparked by allegations that Provisional IRA members were involved in the murder of Belfast man Kevin McGuigan Sr that month.

But pressed as to whether the RHI scheme was discussed with him that summer, he says he can't rule it out.

He's "absolutely clear" that he didn't give an order that cost controls would not be added to the scheme or for them to be delayed until the latest date.

The DETI minister's adviser Tim Cairns emailed Timothy Johnston in mid-August 2015 to say that they needed to "get a catch-up" on the RHI scheme.

"If we are to deviate from GB policy it will require a ministerial direction," he wrote - a ministerial direction is a formal instruction to override concerns from civil servants.

Image source, RHI Inquiry

Sir Patrick Coghin says that's a "pretty clear suggestion that somebody, somewhere was saying" that cost controls should not be added to the scheme.

He reminds the witness that Mr Cairns's evidence is that Mr Johnston told him that cost controls wouldn't happen.

Mr Johnston reiterates his denial that he was involved in discussions about the RHI that summer.

Inquiry panellist Dame Una O'Brien wants to know whether Dr Andrew Crawford was the "de facto" DETI ministerial adviser during the summer of 2015 even though he'd left the department.

Dr Crawford had previously served at DETI when Arlene Foster was the minister but he'd moved with her to the finance department in May 2015.

The inquiry heard on Friday that Timothy Johnston told the new DETI adviser Tim Cairns to refer to Dr Crawford on matters he needed help with.

Image source, PA

But Sir Patrick Coghlin says Dr Crawford had even gone so far as to take part in "negotiations" about the RHI scheme that "his minister knew absolutely nothing about".

Mr Johnston says it's too strong to describe Dr Crawford as the "de facto" DETI adviser but he acknowledges that issues for the department would've been referred to him, given his previous experience.

"Here was somebody who had vast knowledge and experience who could be tapped into," he says.

Timothy Johnston says that by not reading a key document about the RHI scheme in July 2015 he missed an opportunity to change how the initiative was handed.

On Friday, the inquiry heard that he'd received a ministerial paper that had been drawn up in DETI, explaining that the scheme was running over its budget and outlining proposals to address that.

It was sent to him by his fellow DUP adviser Dr Andrew Crawford (below) but Mr Johnston claims he didn't read it and the RHI "wasn't something that I had any interest in".

He says he wouldn't have been dipping into "deep departmental issues like that" unless they affected other departments or were the source of a "political row" in the Stormont executive.

But he says "it is very possible" that he would've asked more questions if he'd read it because he would've found out about the scheme's difficulties.

It would've been "much more difficult to float above it all".

Although he shies away from the public eye, Timothy Johnston has long been regarded as the primary behind-the-scenes influence in the DUP and last year he became the party's powerful chief executive.

In the days when the party opposed David Trimble's Ulster Unionists, he was its communications director, working particularly closely with Peter Robinson.

He was involved in the negotiations around the St Andrews Agreement that led to the restoration of devolution in 2007 and was an adviser at Stormont Castle for Ian Paisley, Peter Robinson and Arlene Foster.

Image source, Press Eye

The Paisley family publicly blamed him for compiling a critical survey about Dr Paisley's leadership before the party founder resigned - it was a claim Mr Johnston said was regrettable and inaccurate.

He is one of the DUP advisers that Jonathan Bell claimed would not allow the RHI scheme to close in early-autumn 2015 but he has rejected that allegation.

As an adviser to Arlene Foster, he was paid the maximum salary allowed for the job - £91,809.

When he appeared at the inquiry on Friday, Timothy Johnston acknowledged that the party's ministerial advisers were not always appointed in line with regulations.

Mr Johnston - himself a former adviser who worked with three Northern Ireland first ministers over a 10-year period - said there had been a "drift away" from the proper procedure.

Image source, RHI Inquiry

Inquiry chair Sir Patrick Coghlin suggested that the DUP ignored the rules in an attempt to "centralise power".

Mr Johnston is back in the witness chair today to complete his evidence and you can find his written statements to the inquiry here, external and here, external.

Image source, RHI Inquiry

The DUP's chief executive Timothy Johnston is in the witness chair and the inquiry barrister Donal Lunny is posing the questions.

Press play on the video at the top of this page to watch the proceedings.

Jayne McCormack
BBC News NI politics reporter

Image source, RHI Inquiry

The Charity Commission is "carefully considering" claims that a renewable heat group may have misled an investigation linked to the RHI scheme that it conducted.

It follows Wednesday's evidence at the RHI Inquiry, when Michael Doran of the energy efficiency charity Action Renewables gave evidence.

With Patsy McGlone's evidence at an end, the inquiry takes a break.

It'll be back at 14:00 when the DUP's chief executive Timothy Johnston will be answering questions.