BBC News Northern Ireland

Well, where to start? Thursday was a day of revelation after revelation, giving a real taste of what's to come in the months ahead.

The inquiry heard that DUP advisers worked to stop decisions being taken about the RHI scheme as it came under huge budget pressure.

One adviser - Andrew Crawford - was able to predict the spike in applications that led to the £700m overspend, and he shared sensitive internal emails with family members, one of whom later benefitted from the scheme.

It was also told that the then finance minister Arlene Foster made a late attempt to delay the already belated introduction of measures to control the cost of the scheme on behalf of a constituent.

Read our summary from yesterday here, or you can go back over our live updates from that session here.

BBC News Northern Ireland

An independent inquiry into the RHI scandal was established in January 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 this week and Sir Patrick Coghlin (above), a retired Court of Appeal judge, is its chair and has been given full control over how it will operate.

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 last year.

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, and as we near a year on from that Northern Ireland remains without a devolved administration.

There were critical flaws in the way the RHI scheme was set up that left it open to abuse and that later saw its budget spiral out of control.

Crucial cost curbs that existed in a similar scheme in Great Britain were not replicated and claimants could effectively earn more money the more fuel they burned.

That was because the subsidies on offer for renewable fuels were far greater than the cost of the fuels themselves.

As a result, the scheme racked up a huge projected overspend - £700m at the most recent estimate - and the 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.

Few people, if anyone, would have expected it to have the consequences it has done in the months that followed.

It 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 a sparkling clear autumn day up on the hill at Stormont and we've reached the final day of the opening week of the RHI Inquiry.

Image source, Press Eye

The inquiry's senior counsel David Scoffield QC has completed much his lengthy opening address - the last part will come next week.

Today, we'll hear opening statements from the inquiry's core participants - the Department for the Economy, the Department of Finance, and Ofgem, which administered the RHI scheme.