The sole matter described as urgent in Mr Hutchinson's (below) handover was a review of the RHI scheme's tariffs.

Mr Aiken says that wasn't considered at all until "potentially the start of 2015".

Image source, RHI Inquiry

Mr Hughes says it's probably reflective of his work on the domestic RHI scheme and the knotty problems of Carbon Trust loans and data sharing with the RHI scheme administrator Ofgem.

"There was no scope, or no time to do anything else," he says.

He did have a meeting with Mr Hutchinson in August 2014 but the non-domestic RHI scheme "wasn't touched on in the meeting at all".

After joining the RHI scheme team in June 2014, Mr Hughes was given a handover document by Ms McCay, who had been working on the project in a temporary role.

It was originally put together the previous month by Mr Hutchinson, the DETI official who had been most hands-on in his work on the scheme from its inception in 2011.

Image source, Getty Images

It listed "immediate actions" that Mr Hutchinson felt had to be addressed by the end of August 2014, including the consideration of a way to adjust the subsidies on offer in order to prevent excessive payments.

In her evidence on Tuesday, Ms McCay said she quickly realised that "there just wasn't time" to get through all of it in the suggested timeframe.

Mr Hughes agrees: "There was a lot of stuff on that list and we certainly weren't going to get it done by the end of August."

The team working on the RHI scheme was "clearly... very, very under-resourced", says Mr Hughes.

In his near 40-years working in the civil service has never dealt with anything as complicated as that heat initiative.

Image source, Getty Images

Mr Aiken puts it to Mr Hughes that the large turnover in staff wasn't helped by the nature of the handover process.

"Not only was the whole team changing but the changeover was being done through someone (Davina McCay) acting up in one of the posts for a six-week period" he says.

It was "very, very unusual" for there to have been so many changes to staff at the same time as happened on the RHI scheme in 2014, says Mr Hughes.

The issue of staffing is one of the key themes of the inquiry, and Mr Hughes says the high turnover of people working on the initiative during a key period in its lifespan and the lack of continuity "significantly contributed to the problems that arose".

Image source, RHI Inquiry

"The whole team was different - they were all new, so there was no link back to the past, really."

In his written witness statement, Mr Hughes said the changes were "unprecedented".

"I am a civil servant with almost 36 years service across a number of departments and I have never encountered this level of staff change at the same time in any division before."

Asked what knowledge he had of the RHI scheme when he joined DETI in June 2014, Mr Hughes says: "Absolutely nothing at that time."

He was appointed as a deputy principal on the team working on the scheme, mostly focusing on the day-to-day running of the domestic scheme but later splitting his time between it and the non-domestic initiative.

Image source, RHI Inquiry

That was the same level of position held by Peter Hutchinson, who worked on the scheme from its outset until he left in May that year.

Mr Hughes says that in spite of his lack of knowledge about the project he was up for the challenge.

"Congratulations to all who made it this morning," smiles inquiry chair Sir Patrick Coghlin as he opens proceedings.

Junior counsel Joseph Aiken congratulates Mr Hughes for braving the feared snowstorm - the Beast from the East - to make it up the hill here at Stormont.

Image source, RHI Inquiry

Mr Hughes has had a long career in the civil service dating back to 1981 when he joined the old Department of Commerce, a predecessor of DETI and what is now the Department for the Economy.

Having since worked in other departments, including a spell in the Department of Agriculture and Rural Development, his career came full circle in 2014 when he joined DETI.

Mr Hughes's witness statement is available on the inquiry's website, external.

BBC News Northern Ireland

Former DETI minister Arlene Foster and senior civil servants knew the department delivering the RHI scheme was "badly under resourced" but still decided to go ahead with the project, the inquiry heard.

Image source, RHI Inquiry

David Thomson, a retired former senior manager at the department, said there was a staff shortage in a "critical area".

He also said the initiative "wasn't ignored" by DETI's top management team but bosses and the minister decided not to make it a priority.

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, 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.

The wintry weather is setting in on the hill at Stormont, but we've made it up to Parliament Buildings - let's hope the usual RHI crew have all been able to do so too.

We have a new witness today - civil servant Seamus Hughes who joined the Department of Enterprise, Trade and Investment's (DETI) energy division in June 2014.

Proceedings begin shortly, and we'll have the usual live stream and text commentary.