Mr Aiken asks the witness why there was a "dilution of the level of risk that the minister may face" in relation to the RHI scheme.

Sir Patrick says that Mr Bell should've been told that the scheme posed a risk, rather than being given the impression that it could be handled with "sidestepping... in order to gain funds".

Image source, RHI Inquiry

"There isn't any other way of reading this submission," the inquiry chair adds.

Mr Wightman says his job was "quite high-pressure at the time" and he took direction from his superiors about changes they wanted made to the submission without thoroughly challenging their suggestions.

"Normally I would challenge it," he says, "but... there was an awful lot of trains in motion."

Sir Patrick sums up in a nutshell the situation regarding the edited submission that was sent to the then enterprise minister Mr Bell.

"The end result of this," he says, "is that the minister gets a submission which has been changed with the knowledge and/or the direction of the senior members of DETI in such a way that it is false."

Image source, Pacemaker

Changes to the submission to Mr Bell (above) made for a "significant downplaying of the need for concern" about the RHI scheme, according to Mr Aiken.

And that point is accepted by Mr Wightman.

He says his initial drafts were "certainly a bit more stark and a bit more up-front" in the information they contained for the then DETI minister.

A passage that explained that DETI would have to cover any shortfall in funding for the RHI scheme was taken out of the final submission to the minister.

It stated that the money "may have to be... taken from other investment programmes".

DETI had been warned in 2011 that there would effectively be a penalty imposed of about 5% in the case of an overspend.

Sir Patrick says that by taking that passage out it "removes... any concern" about the penalty - it's another point that Mr Wightman accepts.

Wording used in the July 2015 submission to the minister about the RHI scheme would not have given him a "true reflection of the risk that the department faces as known by the officials", says Mr Aiken.

Mr Wightman admits that it wasn't made clear to the minister that the overspend on the scheme would have an impact on DETI's overall budget.

Image source, RHI Inquiry

In fact, the minister was told that it would not have a direct impact on the budget.

The witness says he made the changes "on instruction from somebody else" and he agrees that what the submission contained could be "misleading".

Inquiry chair Sir Patrick Coghlin is concerned about why the "convincing reason" for seeking extra funding for the RHI scheme - the fact it was running twice over its allocated budget - was removed from the submission to the minister.

He says its hard to understand why Mr Wightman doesn't remember why it was removed.

Image source, RHI Inquiry

"It's just such an obvious omission, unless it is in some way influenced by guilt or concern that this has got to this stage, from Mils or Stewart or whoever it was," Sir Patrick says.

Mr Wightman says he'd be "very surprised" if he'd made the changes without speaking to his superiors.

Mr Aiken runs through the amendments made to the draft on on 7 July.

"Why not communicate to the minister that we've only got half of the money we need?" he asks, referring to a change to the document that appears to have been made to Mr Wightman.

Image source, Getty

The witness says the changes were made in "quite a complicated couple of hours".

He says he was speaking to his superiors and he can't be sure whether it was DETI energy boss Mr Mils or Chris Stewart, the minister's adviser, who suggested the amendment.

Image source, Getty Images

It was not "spelled out" in the submission to the DETI minister that the RHI scheme was paying out more to claimants than had been intended, says Mr Aiken.

The department had started work on how to address the issue of overcompensation and the inquiry barrister asks why that wasn't drawn to Mr Bell's attention.

Mr Wightman accepts that there was an opportunity to tell the minister that the department was looking at review whether the scheme was value for money.

Mr Wightman's team had been pursuing the Department for Energy and Climate Change (DECC), which operated a similar RHI scheme in Great Britain, for clarification of how the initiative was funded.

As he puts it, they were still "going on a goose chase with DECC".

Image source, Getty Images

Mr Aiken turns to the second draft of the submission sent to senior DETI management by Mr Wightman on 7 July 2015.

It included a copy of the email Mr Wightman's boss John Mills sent to DECC that day asking for an explanation of scheme's funding arrangement - that email didn't get a reply until a month later.

First on the agenda today is a submission sent to the then DETI minister Jonathan Bell on 8 July 2015, which highlighted that there were problems with the RHI scheme and its budget.

The first draft of the submission was drawn up by Mr Wightman two days before and it outlined that expenditure on the RHI scheme in 2015-16 would be £23m, "almost twice" what the department had available to spend on it.

Image source, Getty Images

But by the time the submission got to the minister, the language was "very different", as Mr Aiken puts it, with the "strength of the language" changing - a theme that continues throughout the document.

It stated: "We are currently seeking extra funding as forecast scheme expenditure exceeds previous funding allocations."

Mr Aiken points out that it doesn't convey the same message as the first draft and Mr Wightman accepts that's a fair point.

Stuart Wightman takes his seat for another all-day session - his fifth appearance before the inquiry.

He headed DETI's energy efficiency branch from June 2014, meaning he had oversight of the RHI scheme.

Image source, RHI Inquiry

He first appeared before the inquiry back in March and his most recent visit was this month.

He's reassured by the inquiry's junior counsel Joseph Aiken that today and tomorrow will be the last times he'll have to answer questions in front of the inquiry panel.

You can have a look at Mr Wightman's written statement on the inquiry's website, external.

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 and what was then a developing political crisis surrounding the scheme.

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

Image source, Pacemaker

It will look 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 2015
• the scheme's closure

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, PA

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, a year-and-a-half 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 it 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.

The most recent estimate for the overspend was set at £700m, if permanent cost controls aren't introduced.

The massive overspend bill 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... and 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 businesses 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 Stormont for the return of the Renewable Heat Incentive Inquiry after a week without evidence sessions.

The sky over Parliament Buildings is a little bit more grey than we remember it during the heatwave when the inquiry was last sitting but it's still pleasant up here on the hill.

Image source, AFP

Back in the inquiry hotseat today is Stuart Wightman, who oversaw the running of the RHI scheme when he was the head of the Department of Enterprise, Trade and Investment's (DETI) energy efficiency branch.

It all kicks off shortly and we'll have live updates and the video stream throughout the day - stick with us.