Most new presidents find settling into the White House a disorientating experience. Nothing can prepare a person for the pressure and isolation, and afor being the relentless focus of national and international interest. Unless you have served as a presidential advisor or vice president, no previous experience can give you an insight into, let alone prepare you for, being President of the United States of America.

Donald Trump’s failure to deliver comprehensive healthcare reform within sixty-five days of assuming the presidency is not a huge surprise. Despite the fact that the Republican party controls not only the White House, but the House of Representatives and the Senate as well, there is a vital lack of common understanding of what a new healthcare policy should look like inside the party.

Business people often think that if politics and government could be more like business then public administration would be much more efficient and effective. But the fact is that no business is as publicly accountable or as complicated as a government, with the responsibilities and expectations that voters and taxpayers place on it.

The president has learned the hard way that the techniques of successful business practice are not, on their own, sufficient to meet the challenges of politics. He has plenty of time to learn the lessons and recover his mojo, but his failure holds three vital lessons for the Brexit negotiations that lie ahead of Britain and the European Union.

1. Do not over-promise and under-deliver. Throughout the election campaign Donald Trump made repealing Obamacare his number one priority. He promised “repeal and replace” – a catchy slogan that caught many people’s imagination and mood. At no point was there ever any serious policy work undertaken by his team to see what a replacement would look like. When it came to it, the president was left mediating between different factions of the Republican party without any concrete proposals of his own. He hugely over-promised action in an area where he had done no original thinking.

2. Do not let rhetoric and hyperbole race out of control. In his desire to fire up his base and win the election, Donald Trump used healthcare reform as a battering ram to assault what he viewed as the prevailing out-of-touch political consensus in Washington. The fact is that most politicians in Washington – as in Westminster – are acutely in touch with the political mood in their constituencies and amongst their electorate. It is a myth to suggest politicians are “out-of-touch”. Their fortunes rise or fall by responding to and interacting with prevailing popular and political moods. Donald Trump’s rhetoric has far outpaced his ability to deliver change. Care needs to be taken in Britain to ensure public expectations do not become unaligned with what can be achieved in the Brexit discussions.

3. Master the detail. The detail of any political deal is key to its success. Leaders may campaign in slogans but they govern by detailed policy settlements. The Brexit negotiations will be the most substantive and detailed since the end of the Second World War. It is vital for everyone in the United Kingdom that the detail is negotiated robustly and pinned down. Every one of us in every area of our lives will be affected by the Brexit negotiations. The next two years will demand a level of stamina, patience and maturity unparalleled in the modern era. Donald Trump had no healthcare policy of his own to offer, and when he tried to split the difference between the various sides in the discussion, he found that as soon as he had won over one new group he lost another. Mastering the detail is a way to win points in discussion, build confidence in the process, and help build the broadest possible political support for the undertaking.

Britain has a highly experienced and steely prime minister who loves detail. She is the right person, in the right job, at the right time. She has good people around her, and she is going to need them. For much of the next two years those conducting the negotiations are going to face some of the toughest scrutiny and pressure faced by any politician since Margaret Thatcher made the courageous and lonely decision to despatch a naval task force to the South Atlantic in 1982.

Meanwhile the country has to be governed. Northern Ireland and Scotland pose continuing challenges, the normal day-to-day business of government has to be conducted, and there will be the unexpected things  – there are always the unexpected things in government – that force their way on to the government’s agenda and the prime minister’s desk.

Moments of great national impact, such as last week’s Westminster attack, provide unsought and unexpected moments for our national leaders to speak, to lead, to build their relationship with us. Speaking about the tragic and distressing events, the prime minister caught the mood and embodied the national sense of resilience perfectly. Along with home secretary Amber Rudd and House of Commons leader David Liddington, who on the day of the attack displayed exemplary leadership in the chamber, the prime minister showed her inner strength. We have learnt more about the prime minister, and it bodes well for the weeks and months that lie ahead.