Junior counsel Donal Lunny is asking the questions today and he picks up where he left off with Dr Edmund Ward (above) on 16 March.

Back then, Dr Ward - from the RHI scheme administrator Ofgem - told the inquiry that the level of oversight of the RHI scheme in Northern Ireland was nothing like that in the parallel initiative in Great Britain.

Image source, RHI Inquiry

You'll find Dr Ward's written statement to the inquiry in full here, external.

Hold on to your hat - this could get rather technical.

BBC News NI

Civil servants at DETI tried to suspend the RHI scheme as the "penny dropped" that the budget was under huge pressure, the public inquiry was told.

They asked the administrator Ofgem to "queue" new applications while they worked out the budget position.

Image source, Pacemaker

Ofgem was worried that the bill for its work might not get paid and also had concerns that it had commitments to scheme applicants and might end up getting sued.

DETI's request to pause the applications came when it's monthly payments to scheme claimants had gone from £264,000 in March 2014 to £1.5m in June 2015.

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, 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 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.

Image source, PA

Welcome along to Friday's live coverage of the Renewable Heat Incentive Inquiry from a blustery Stormont

We've a familiar face in the hotseat today - witness Dr Edmund Ward was the head of Ofgem's technical team.

He appeared at the inquiry back in March and if you're a real nerd and followed our Stormont Live service you may remember him giving evidence to the Northern Ireland Assembly's Public Accounts Committee inquiry into RHI in October 2016.