"Everybody knew" that an important review of the RHI scheme that was supposed to have been carried out in 2014 hadn't been done, says Trevor Cooper.

It had been a condition of the original approval of the initiative that it would be regularly reviewed, providing the opportunity to spot problems and get them rectified.

But in a business case for the changes to the RHI scheme that it submitted to the finance department, DETI claimed a review had been done in October 2013.

Image source, RHI Inquiry

Inquiry barrister Joseph Aiken says there are a number of occasions such as that when things that are "just not accurate" were not corrected.

Incorrect information became the "accepted language" within DETI and is presented as a "statement of fact" in material given to the Stormont department that's the "gatekeeper to the funds", he adds.

Mr Cooper accepts that shouldn't have happened.

There were as many as four projects a year under DETI's responsibility that were spending public money without the necessary approval, reveals Trevor Cooper.

He says the department had to seek retrospective spending approval on those projects.

Image source, Getty Images

He puts the number in context, saying there there were "literally hundreds" of programmes and projects.

The former senior finance official agrees with Dame Una O'Brien when she says that the RHI wasn't the first time in his career that he'd had to deal with a lapsed spending approval.

DETI could not try to pass off "as a one-off gaffe" the fact that the RHI scheme was spending money without finance department approval, wrote a senior economist in the department in June 2015.

That was because it came "hot on the heels" of the discovery that the same thing had been happening with separate project linked to the department.

Inquiry panellist Dame Una O'Brien says it contrasts with the evidence of David Sterling, the head of the Northern Ireland Civil Service, who said the RHI was something of an isolated incident.

Image source, RHI Inquiry

Inquiry chair Sir Patrick Coghlin says it's a matter of concern that a number of big projects, not just the RHI, had not gone well at DETI - he can think of "three one-off gaffes".

"There has been a very firm assurance from the top that all this is now sorted out, all this is fine," he says.

He adds that the panel will have to make recommendations on a more general level of how the civil service operates, not just in relation to what went wrong with RHI.

Trevor Cooper says he was "worried" in June 2015 about how spending on the RHI scheme could be controlled.

But Sir Patrick Coghlin pulls him up on that, asking whether the civil servant had been as cognisant of the need for spending controls in the scheme back in 2011 when it first came across his desk.

Back then, Mr Cooper didn't check the scheme had controls - there was no power to suspend it, even though he thought there it had a "big red button", as he told the inquiry when he first appeared in February.

Image source, RHI Inquiry

Mr Cooper chaired an internal DETI scrutiny panel that assessed the scheme before it was opened in 2012 and part of its responsibility was to tell Stormont's finance department about whether or not the RHI had adequate spending controls built into it.

It simply took the word of a civil servant that the scheme could be halted if it looked like it was at risk of going over its budget.

It's Sir Patrick's view that the scrutiny panel's function was "not effectively done" because its members didn't examine the scheme's regulations to see if any spending controls existed.

"There was no effective budget control in the regulations - it's as simple as that."

It was a "pretty big problem" when Trevor Cooper found out that DETI had been spending public money on the RHI scheme without approval from Stormont's finance department.

The scheme's original spending approval was to last until March 2015 but officials failed to get it renewed after that date.

Image source, RHI Inquiry

That's wasn't the only issue with the scheme at that stage - the budget had already been blown and there were controls problems, as the inquiry heard yesterday.

Mr Cooper found out about the lapsed spending approval in June 2015 - he says the RHI was the biggest problem on the table at the time but he admits "no-one appreciated where it would end up".

As the legal teams and the witness take their seats, inquiry chair Sir Patrick Coghlin can't help making one of his regular digs at the dodgy heating system in the Stormont Senate chamber.

"We've been discussing the autumnal beauty of the scene outside (below) but when you walk in here again it's summer," he quips.

Image source, PA

Meanwhile, inquiry counsel Joseph Aiken, who's fond of a cricketing metaphor or two, assures today's witness Trevor Cooper that his time in the inquiry hot seat will be over "by close of play" today.

As a reminder, Mr Cooper was a senior finance director at DETI - the microscope is focused on his role in how the RHI's financial problems were handled, particularly in the spring and summer of 2015.

He's submitted several witness statements to the inquiry - you'll find them here, external.

Jayne McCormack
BBC News NI politics reporter

There was a "total lack of communication" between two divisions of the Stormont department that was running the RHI scheme, the inquiry heard.

Chair Sir Patrick Coghlin made the comment during evidence from senior DETI finance official Trevor Cooper.

Image source, Pacemaker

The inquiry heard evidence suggesting there was insufficient sharing of information between the enterprise department's energy branch, which drew up the scheme, and the finance branch.

Sir Patrick described it as "such dysfunction" and Mr Cooper said he couldn't disagree with that.

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 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 will operate.

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 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, well beyond 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 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.

Image source, Getty Images

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.

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.

It's been the first morning of scraping ice off the car windscreen for many people but it's turned into a beautiful morning up on Stormont hill.

Now safely holed-up in the BBC bunker in the bowels of Parliament Buildings we're ready to bring you Thursday's action from the Renewable Heat Incentive Inquiry.

There's a familiar feel to today's proceedings as we'll be rejoined by Trevor Cooper, the former head of finance at the Department of Enterprise, Trade and Investment (DETI).

The session starts shortly - stay with us for live video throughout the day and text reporting on all of the important bits.