David Davis knew he had a choice to make. Either to be in contempt of parliament for deliberately failing to provide full disclosure on his department’s Brexit impact assessments. Or to own up to incompetence and laziness. No contest. Incompetence and laziness won hands down. For one thing, they had the virtue of truth. For another, he was just too lazy and incompetent to do anything else.

This was the moment that the Brexit secretary had to come clean. Summoned to explain to the select committee why it had taken him three weeks to hand over a couple of lever arch files – junior barristers are better prepared for defending shoplifters at Horseferry Road magistrates court than the government appears to be for Brexit – Davis was at his sulkiest, snarkiest best, sucking loudly on a sweet throughout.

The committee chair, Hilary Benn, looked unimpressed. Like a schoolteacher who has finally lost patience with his stupidest pupil. Why had it taken so long for him to hand over the reports? Davis shrugged. Because the dog had eaten his homework. Because it had taken him three weeks to cobble something together once he realised that what he had thought existed didn’t exist after all. The committee could take its pick.

So, had the government undertaken any impact assessments? No. Why should they? Davis pouted. Benn took a deep breath, trying to contain his irritation. Because everyone in government had kept saying they had. Including Davis, who had claimed they existed in excruciating detail.

“We are looking at the effect …” Davis mumbled. “I mean … do not draw the conclusion that because you use the word impact that you have written an impact assessment.” Or have done anything at all, in fact. Brilliant. Just because he had said he had written some impact assessments, there was no reason for anyone to believe him.

Q&A If David Davis is held in contempt, what are the implications for him? Show Sanctions for contempt of parliament have not been used in modern times so the potential consequences for David Davis are not entirely clear. Erskine May, the guide to parliamentary procedure, says that an member of the Commons can raise a privilege complaint with the Speaker. The Speaker then has the discretion to decide whether the complaint should be put to the House of Commons. The MP complaining can then table a motion formally calling for the alleged breach of privilege to be referred to the House of Commons committee on privileges, which would consider sanctions. The Institute for Government wrote last year: "Historically, those found guilty of contempts could be fined or imprisoned, but those sanctions have not been used by the Commons since 1666 and 1880 respectively. For all sorts of practical, legal and constitutional reasons, it is highly doubtful that the modern House would seriously consider this.”

Besides even if he had written some impact assessments they would probably have been a bit rubbish as most forecasts were always wrong, so it was probably better that he hadn’t bothered. Just behind him, Davis’s advisers were in a state of mini collapse. Their expressions, pure pain. Quit while you’re no further behind, they begged him.

‘Like a schoolteacher who has finally lost patience with his stupidest pupil’: The Brexit select committee chair, Hilary Benn. Photograph: Christopher Thomond/The Guardian

Davis ploughed on, too dim to realise he was about to contradict himself. Yet again. “These folders … ” he said, proudly pointing towards the two files that he had just admitted were basically full of mindless, anodyne drivel. “These folders represent 15 man years of expert work.” That explained the country’s productivity crisis.

There was a moment’s silence while everyone tried to absorb the Brexit secretary’s seeming indifference not just to truth but to any objective reality. It was possible he was even dimmer than they had given him credit for. Benn chose to give him the benefit of the doubt.

Would he like to explain why the government hadn’t done any contingency planning when it had originally intended to get to the second phase of the Brexit talks back in October? Davis wouldn’t. Though he could probably hazard a guess that he hadn’t bothered because he had never imagined the talks progressing before the new year anyway. Slow and unsteady wins the race.

Once Benn had given up the unequal fight of finding sentient life in the Brexit secretary, he let Labour’s Seema Malhotra have a go. She went forensically through the times and dates when parliament had been assured the impact assessments not only existed but were of the highest quality, but was met with only incomprehension by Davis. What bit of Schrödinger’s impact assessments did she not get? There and not there. Stephen Timms went for a simpler approach. How many pages of the reports had been withheld because they were confidential? Davis looked blank. He didn’t know because he hadn’t read them.

Sensing their man was not waving, but drowning, several Tory Brexit hardliners tried to come to his assistance. There must be other material that hadn’t made it into the folders, they said. Not really, Davis said, declining the helping hand. Did the EU have such detailed contingency planning? “Not on a similar scale,” Davis said confidently, unconsciously telling the truth. The EU have done more. A lot more.

Even Jacob Rees-Mogg got in on the act. Normally the Tory MP prides himself on putting parliament above party politics. Not this time. Last week he had castigated Davis in the Commons for failing in his duty; now he was fawning in his praise for the minister’s generosity in providing such riches. Rees-Mogg’s silver sword of truth began to look somewhat tarnished.

Long before the end, Davis got visibly twitchy, frequently reminding everyone he had another appointment, despite having been told to prioritise the committee. Benn asked one last question. Had the government done any planning before deciding to leave the customs union? “Oh no,” he said breezily. Don’t be silly. Brexit was no biggie. Was that all? Right, he’d be off then. Some might have called it a dereliction of duty. If there had been any sense of duty to start with.