Arlene Foster's Spad privately said RHI cash should be '˜maximised'

Andrew Crawford, who is accused of working in the shadows to delay cost controls at the time when the scheme was out of control and when some of his family members were installing RHI boilers, made the comment in October 2016, just a month before the ‘cash for ash’ perverse incentive was finally ended, Dr McCormick said.

Dr McCormick said that he had met Dr Crawford at an annual dinner and during their conversation the DUP man “confirmed that he had been of the view that there was no good reason against maximising uptake of the RHI scheme and hence the HMT funding”.

Dr McCormick said: “On approaching Andrew Crawford, I knew our conversation would touch on the RHI, so I began with a deliberately disarming comment to the effect that ‘you did warn me about the abuse of the scheme’ – referring back to [another conversation].

“Andrew Crawford’s response, which he volunteered very clearly, was that his view had been that, because the scheme was funded from AME, it was actually desirable for Northern Ireland participants to maximise the return from it – i.e. a very similar line to that in his email of 20 July 2015 to Timothy Cairns.”

That inquiry – which has already been published by the inquiry – was sent as the scheme ran out of control in 2015.

Dr Crawford wrote to Mr Cairns, a fellow DUP Spad that breaching the RHI budget could be a positive. He said: “I am a little confused over what the problem is… if we go over our 4% target all that will happen is that we will get more than our fair share of the UK pot…I would have thought that this is to Northern Ireland’s advantage”.

The day that senior civil servants realised the entire overspend was coming from Stormont’s budget was “a day of complete dismay”, one official told the inquiry.