The growing sense that the us presidency is slipping from the grasp of donald trump will be greeted with quiet relief in most of the government offices of western europe. but not, perhaps, in london.

The johnson government is desperate to demonstrate the benefits of leaving the eu and mr trump has always been vociferously pro-brexit. he has also promised the uk a great trade deal. by contrast, democratic candidate joe biden, who has irish roots, has warned there will be no trade deal with the us if the uk violates the good friday peace agreement in ireland a comment that was greeted with shock and anger by the conservative right.

But any quiet longing for a second trump term in downing street, or in the tory party, rests on a profound misunderstanding both of british interests and of the likely nature of another trump administration.

Talk to people who have worked closely with the us president and you will hear warnings that, if mr trump battles his way back to health and back into the white house, his second administration would be much more radical in its foreign policy and much more coercive towards the uk.

There would be no more tolerance of gentlemens disagreements over sensitive topics such as iran, israel, china, climate change, the international criminal court or the world health organization. instead, the full range of us power would be brought to bear on london to force the uk into line.

A taste of these tactics came in the recent dispute between the trump administration and the johnson government, over whether huawei, a chinese company, should be allowed to supply 5g telecoms to the uk. when the british announced a deal favourable to huawei, the us quickly threatened to curtail intelligence sharing under the five eyes arrangement. unsurprisingly, the johnson government changed course.

The uk-us intelligence relationship is at the heart of the special relationship. but there are plenty of other british weaknesses that the us could target. the uk is vulnerable to the sanctions and tariffs that the trump administration is increasingly using as its preferred tool in foreign policy disputes.

Those who imagine that mr trump would never deploy these tactics against the british are kidding themselves. this is an administration that has not hesitated to threaten tariffs or sanctions on both japan and germany which are, in strategic terms, more important allies than the uk. mr trumps own relationship with britain is, in the words of one of his former aides, remarkably superficial and does not extend much beyond an interest in his golf courses and dinners at buckingham palace.

There are also plenty of areas of foreign policy where the uk continues to diverge from the current american line, to the increasingly open irritation of the trump administration. when the uk sided with germany and france in resisting new sanctions on iran, mike pompeo, us secretary of state, accused it of supporting the worlds largest state sponsor of terrorism.

While the trump administration has embraced america first unilateralism, the uk has remained committed to internationalism. it has significantly increased funding for the who, in response to the withdrawal of american money. it is also chairing the next stage of the un climate talks, from which the us has withdrawn. and while the us has imposed sanctions on the iccs chief prosecutor, the uk remains a member of the court.

A second trump administration, emboldened by retaining the white house, would be much less patient about these policy divergences. it would demand loyalty from the uk and, if that was not forthcoming, pressure to fall in line could be ramped up quickly.

Some in the johnson government might regard these indignities as an acceptable price to pay for that elusive trade deal. but there remain formidable obstacles to the achievement of any deal not least the oft-stated british reluctance to accept american food standards. even if an agreement is achieved, it will struggle to get through an increasingly protectionist congress. and even if the deal is ratified, the uks own estimates of the economic benefits are unimpressive. perhaps the us might chuck in an honorary degree from trump university for boris johnson, to sweeten the deal?

The conservative partys fear of mr biden is also wildly excessive. the irish-american community is firm in its defence of the good friday agreement which is, anyway, strongly in the uks own interests. but it is not the anglophobic force imagined by tory backwoodsmen and anyway irish-americans are well-represented in both the republican and democratic parties.

Mr biden is a multilateralist, strongly committed to american alliances. his foreign policy advisers are drawn from the east coast elites, which have strong cultural and educational ties to the uk.

By contrast, a second trump administration would be devoid of the establishment types who initially softened the edges of mr trumps foreign policy. radicalised by victory, the us president and his acolytes would launch a new assault on the liberal world order.those tories who complained that brussels was turning the uk into a vassal state would discover a more pressing threat from washington.