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For a famously genial minister, the Brexit Secretary David Davis seems to have developed the art of upsetting MPs with doubts about Brexit into a science.

Today he faced accusations of misleading Parliament and "gross negligence" after he told MPs the government had so far made no attempt to calculate the potential effect of leaving the EU on British business.

MPs on the Brexit select committee professed their bewilderment. One Labour MP later said the Brexit secretary should be "put in the Tower of London for contempt of Parliament".

And Mr Davis seemed to amplify the level of criticism by suggesting the potential impact of Brexit would be so huge as to make any forecast worthless.

Outraged? Baffled? Plenty of people may answer "yes" to both. It is at least arguable that since the outcome of Brexit is still unknown, its effects are incalculable.

The trouble stems from the fact that David Davis had previously told MPs exhaustive work was under way across Whitehall to gauge the potential effect of Brexit across nearly 60 sectors of the economy. That gave the impression of tireless data collection, and painstaking analysis.

Today, his tone could not have been more different. At one point he admitted that one or two of the sectoral studies were simply "not very good" and were sent back to be improved.

He also reminded the MPs that the two lever-arch files, containing some 850 pages, reluctantly compiled and handed over in response to a direct vote of the Commons, contained little not already in the public domain.

Then, Mr Davis offered the "clarification" that none of this work went so far as to forecast the potential cost of differing outcomes.

He said: "I'm not a fan of economic models because they have all proven wrong. When you have a paradigm change - as happened in 2008 with the financial crisis - all the models were wrong.

"The Queen famously asked why did we not know.

"Similarly, what we are dealing with here in every outcome - whether it is a free trade agreement, whether it is a WTO outcome or whether it is something between that on the spectrum - it is a paradigm change."

So whatever the impact might be, it would be enormous. The reaction of MPs was inevitable.

And the conclusion that Britain's route to Brexit is being navigated one step at a time, according to a plan being improvised day to day, hour to hour, is difficult to avoid.