Mr Davis insisted “I do just have to be calm”, revealing that last Monday’s botched attempt at getting an agreement with the European Union to move to Brexit trade negotiations had tested that ability.
Theresa May’s hopes of getting the green light for trade talks were torpedoed at the start of last week by the Democratic Unionist Party, which props up her Government, over concerns that plans for the Irish border could lead to a new frontier being drawn in the Irish Sea.
The Prime Minister was forced into a week of negotiations with the Northern Irish DUP, Ireland and the EU before finally getting a dramatic last-minute deal on Friday, paving the way for trade talks.
Mr Davis said the phone call Mrs May had with DUP leader Arlene Foster last Monday, which appeared to undo the planned deal, was “a lot shorter than people say”, and revealed his patience was tested by events.
The Brexit Secretary told LBC radio: “What’s the requirement of my job? I don’t have to be very clever, I don’t have to know that much, I do just have to be calm.
“And that did test the calmness a bit, a little bit.
“But we had to pick another day and we looked at Wednesday but Wednesday wasn’t long enough for the DUP to sort themselves out so we made it Thursday, Friday morning.”
Mr Davis also said he does not believe economic forecasts as he discussed the furore over the Government’s failure to formally assess the likely impact of EU withdrawal on different sectors of the UK economy.
He was accused of misleading Parliament last week after admitting no impact assessments had been made because their usefulness would be “near zero” due to the scale of change which Brexit is likely to cause.
The Brexit Secretary said: “In the last 18 months I’ve talked about impact here and there, but an impact statement, this is a thing that the Labour Party have been going on about, an impact statement has got a proper meaning in Whitehall, there’s a definition of it and so on, including things like forecasts.
“Now I don’t actually believe economic forecasts, they have all been proven wrong, I mean look at all the ones about Brexit.
“So what we do is we look at what we call a sectoral analysis which is the size of the thing, the size of the industry, employment levels, how much is dependent on Europe, how much is dependent on European regulations, how much opportunity there is in other countries.
“When you know those things, you know what you need to know.”