In late-2016, after the scale of the disaster of the RHI scheme emerged, Stormont called in the professional services firm PwC to conduct an investigation into the matter.

Interviewed by PwC in December that year, Mr Cooper raised some major issues about the scheme.

Image source, Getty Images

Among them were:

• He didn't think DETI's energy team had sufficient engagement with the scheme's administrator Ofgem "that there should've been";
• He believed DETI "thought they had safeguards [in the scheme] that they didn't have";
• He thought DETI "believed that they had the ability to do various things that they didn't have, in terms of stopping [the scheme] and [carrying out] emergency reviews";
• He thought DETI was "fixated on spend - trying to get someone applying... as opposed to monitor the very low numbers that were actually applying at the time".

It's a first appearance before the inquiry this morning for Mr Cooper, so he takes the oath and takes his seat.

For most of the time the inquiry is interested in he was a finance director at DETI.

Image source, RHI Inquiry

Inquiry counsel Joseph Aiken is likely to focus much of his questioning on the role Mr Cooper played as the chair of the department's casework committee that approved the RHI scheme in the early part 2012.

Mr Cooper's written statement can be found on the inquiry's website, external.

BBC News Northern Ireland

An RHI scheme tax write-off should have been part of the information sent to the European Commission in an application for the scheme to be approved, the inquiry heard.

The tax write-off was referred to in emails between two DUP advisers.

Image source, AFP

DETI's EU expert Stephen Moore had to review the application before its submission to the commission.

He said that if he had known about the tax issue, which could've been explicitly prohibited under European rules, he would've "almost certainly" raised it with the Treasury.

BBC News Northern Ireland

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, Press Eye

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, more than a year 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 autumn last year... 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 Friday's live coverage of the RHI Inquiry from Parliament Buildings at Stormont.

As usual, business kicks off in the old Senate chamber at 09:45.

Image source, AFP

Today's witness is Trevor Cooper, who was head of the Department of Enterprise, Trade and Investment's (DETI) finance and EU programmes division.

He's booked in for an all-day session - let's hope he's had a good breakfast.