The first sitting president of the United States to visit Britain arrived here 100 years ago. President Woodrow Wilson came to Britain in 1918 on his way to the Versailles peace conference following the first world war. He came with the most noble of objectives: to help make peace in war-ravaged Europe and to lead the construction of a liberal international order based on laws and rights. Although the global order he was decisive in establishing was rejected at home and later challenged to within an inch of its life by fascism, it survived and was rebuilt more strongly. We are all the beneficiaries.

The contrast between that first presidential visit and the visit of Donald Trump a century later could not be more eloquent of the changing global role of the United States. Mr Trump does not come with a message of peace, as Wilson did, but with messages of conflict and disruption. He arrives not as the optimistic upholder of an international order but as its casual potential destroyer. Where Wilson spoke during his visit of his wish to make right and justice the “controlling force of the world”, Mr Trump arrives in 2018 as the vengeful tribune of might and injustice.

During his 1918 stay, Wilson made a point of travelling to his mother’s birthplace in Carlisle. He also went to Manchester, where he was met by cheering crowds, received the freedom of the city, addressed a lunch in the Midland Hotel, spoke at a public meeting in the Free Trade Hall – and even invited CP Scott, editor and owner of the Manchester Guardian, for an hour’s discussion, a scoop that caused consternation in the US press. It is a sign of changing times that the White House in 1918 could assure Scott that the president “relied on the Guardian’s wholehearted support”.

Better off without it

Mr Trump is never going to get that support today. He is the elected leader of a very great nation, but his arrival here this week is a visit that this country would be better off without. It shames those who offered it so prematurely and foolishly. Little good and much difficulty is likely to come of it. There are many reasons for feeling the unusual sense of outrage and violation that attach to the Trump visit to Britain. Mr Trump’s personal character and behaviour are more than enough reason for many. They certainly belong on any list of objections to his presence here, for he is one of the most unsuitable people to hold his great democratic office in American history. But it is Mr Trump’s politics, his expressed views, his actual actions, and above all his effect and his intentions that are the fundamental issues.

Shamefully, Theresa May rushed to Washington in 2017 to press an invitation on him which he had done nothing to merit

The charge list against Mr Trump is long, unignorable and impossible to tolerate. Morally, it is headed by the racism of the immigration policies he was so proud of in Brussels on Thursday, the cruelty of their enforcement, especially in the separation of children from their parents, the racism to which he gives encouragement at home, and the taunting and visceral threat to the rights and dignities of women, people of colour, and LGBT people, who are all now directly threatened by his latest supreme court nomination. He has ignorantly spurned the threat from climate change, has sucked up to tyrants, has conducted an unprecedented campaign against the free press, launched a trade war, insulted America’s allies, praised America’s enemies and made dangerous mischief in the domestic and regional politics of countless parts of the world. Only this week, heading for Europe, he insulted Germany and said meeting Vladimir Putin would be easy work compared with his meetings in Brussels and Britain.

Over the century there have been US presidential visitors to Britain whose policies were destructive, with whom we did not agree and whose presence here as guests was difficult to navigate. Mr Trump, though, is different. He is unique in his egotistical disrespect for international order and agreement, his overt malice towards long-term allies and institutions, his shameless disregard for truth, and his clear willingness to make trouble and do direct harm to European nations like ours. This puts him into an altogether different category from his predecessors. All these, from Wilson onwards, professed and – less consistently – practised support for international order and rules in which the US was a leading partner and indispensable bulwark. Mr Trump does not.

Play Video 0:46 The moment Trump baby blimp lifts off - video

Threat to liberal values

It is sometimes argued, in defence of the Trump visit, that Britain’s wider interests require us to engage with disreputable and even brutal leaders with whom we may not agree. That is true. But the president of the United States is supposedly our chief ally, with whose country we claim a special relationship, with whom we have shared deep democratic values. When such a leader spits on the foundations of that alliance and actively promotes values and interests which are hostile to ours, the tough lesson of history is that he should not be honoured and must not be appeased.

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Given the threat to liberal values and order that he so obviously represented from the very moment of his election in 2016, Mr Trump should only have been invited to this country after a decent pause and period of careful circumspection. Shamefully, Theresa May rushed to Washington in early 2017 to press a invitation on him which he had done nothing to merit and which made Britain appear, to coin a phrase, a vassal state. She let this country down by doing so. Eighteen months on, the Trump visit is an embarrassment to be endured. Even Mrs May probably knows now that this was a case of invite in haste, repent at leisure. The rest of us should recognise the immense seriousness of this dark turn in our history. We support all those who protest peacefully and with dignity against the presence of a president who is a bad and unreliable ally. Before leaving for Britain on Thursday, Mr Trump told the press: “They like me a lot in the UK.” Fake news again. We don’t like him at all. He is not welcome here.