As minister, Arlene Foster had to approve the consultation document which contained the warning

The first thing is that this shows Arlene Foster’s officials in a somewhat better light.

Civil servants who have been portrayed both by her and by Andrew McCormick as having seriously failed (and in some areas they certainly did) are shown to have actually alerted their minister to the need for cost controls at an early stage in the scheme.

That does not explain why cost controls were stripped out in the first place (which may be the officials’ fault), nor does it explain why they did not put the issue before Mrs Foster by way of an urgent ministerial submission in its own right, rather than as part of this much larger document.

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But it does show that officials at least drew to their minister’s attention that there was a serious flaw in the scheme while it was in its infancy.

The second striking thing about this document is the level of detailed work which civil servants had carried out in relation to introducing cost controls.

It shows that officials expected DETI to introduce the GB system of degression – a form of cost control “in the future”. But they were proposing that a simpler system be put in place immediately on an interim basis.

They noted that RHI “is different in nature to the NIRO [another Northern Ireland-specific renewables subsidy system] in that there is a finite budget for new installations and these budget limits cannot be breached”.

And, foreseeing almost precisely the scenario which developed in late 2015, they warned: “There is always a risk that renewable heat technologies might be deployed in greater numbers than what is forecast and payments exceed expectations”, adding: “Therefore DETI must retain the right to suspend the scheme if budget limits could be breached; however this will only happen at a last resort and, at this stage, is not envisioned to happen.”