Prime Minister Theresa May leaves Downing Street in London after Britain's most senior judges ruled that she does not have the power to trigger the formal process for the UK's exit from the European Union without Parliament having a say. PRESS ASSOCIATION Photo. Picture date: Tuesday January 24, 2017. Ministers are braced for the Supreme Court to decide that Parliament must be given a vote on starting the divorce proceedings. See PA story POLITICS Brexit. Photo credit should read: Victoria Jones/PA Wire Image Credit: AP

United Kingdom Prime Minister Theresa May today becomes the first world leader to meet United States President Donald Trump since he was sworn in last week. The meeting breathes new life into the long-standing ‘special relationship’, with Trump already calling her “his Maggie”, drawing comparisons with the political bond that was forged between former US president Ronald Reagan and former British prime minister Margaret Thatcher in the 1980s.

Despite the many political differences between May and Trump — on the face of it, significantly larger than those between Reagan and Thatcher — both leaders would welcome a constructive partnership that builds on the traditional ties between the two nations founded on demographics, religion, culture, law, politics and economics. For May, the rekindling of this special relationship, in a post-Brexit context, would potentially add some credence to her aspirations for a new “global Britain”, while Trump’s as-yet untested credentials as a leader on the world stage would be burnished.

At the heart of today’s discussions will be setting the early ground work for a potential US-UK trade deal in coming years. This will be a boon for Trump given that he is being criticised, in many quarters, as having the hallmarks of an anti-globalisation, protectionist president, especially after his abrogation last Monday of US participation in the massive, proposed Trans-Pacific Partnership trade and investment deal. At the same time, if May could secure a US trade deal, it would represent a significant win in her battle to show that the UK can, post-Brexit, swiftly secure new trade deals with key economic partners outside the EU.

The mood music will thus be positive between Trump and May on this trade agenda and there are key areas ripe for agreement, including lowering or eliminating tariffs on goods. Equally, however, potential icebergs lie on the horizon, not least given the president’s commitment to “America First”, and the fact that any deal could not be finalised — under the terms of the UK’s membership of the EU — until after the nation leaves the supranational body.

Specific areas of potential disagreement on the trade front include the prospect that harmonising financial regulations between the two countries, with the international dominance of Wall Street and the City of London, will not necessarily be straight forward. Meanwhile, securing agreement in other sectors, including agriculture, where there are also divergence of views and strong interest groups, will not be easy either.

Another key agenda item will be security and defence, which has long been at the core of the special relationship, given the very close partnership between the two nations in the post-war era in areas like intelligence and special forces.

So, while this is a terrain in which there will be much agreement, including over the need to continue the counter-terrorism battle against Daesh (the self-proclaimed Islamic State of Iraq and the Levant), tensions could surface on Nato and Russia in particular.

Trump has repeatedly called Nato “obsolete” and asserted the need for greater burden-sharing of alliance costs between the US and Europe, plus engaged in open political courtship with Russian President Vladimir Putin. However, May is a strong defender of Nato and confirmed earlier this month that the UK would, under its Article 5 responsibilities, come to the aid of any Eastern European country attacked by Moscow, an issue that Trump has so far given much less clear-cut answers to.

May will be keen to find out Trump’s real bottom lines on these issues and, in the words of Thatcher, seek to “stiffen his spine” against what she perceives as the real and present Russian security threat. Part of the reason for her inquiry in this area relate to the mixed messages coming out from him and his senior team in recent weeks.

Trump appears to believe Russia is not a serious threat to the US, and that there is scope for rapprochement, hinting this month that he could drop economic sanctions if the country “is helpful”. Specifically, he perceives there are common interests over issues such as preventing Iran from securing nuclear weapons, combating terrorism and potentially even helping contain a rising China in a new global balance of power.

Yet, US Defence Secretary James Mattis said earlier this month that “Russia is raising grave concerns on several fronts”, including trying to “break the Northern Atlantic alliance [Nato] ... which needs integrated steps — diplomatic, economic, military and the alliance steps ... to defend ourselves where we must”.

Meanwhile, US Secretary of State-designate Rex Tillerson was also forceful in recent weeks in his criticism of Russia.

Already, lack of clarity over US policy towards Nato is one driver spurring EU countries to move towards reversing around a decade of defence spending cuts, totalling around 10 per cent in real terms, which will be welcomed by Trump. Moreover, a new European Defence Action Plan was discussed at last month’s EU summit that, subject to any final agreement, will see greater continental military cooperation.

Given the multiple uncertainties ahead in the Trump presidency, May is likely to seek to play the role today of a trusted, albeit candid, friend in a bid to get close to the president to try to make the relationship work as smoothly as possible. This should provide some protections for bilateral relations in what could be a rocky few years of international relations to come, even if strong personal chemistry fails to take root between the two leaders.

However, while this may be a sensible strategy, at least initially, it is not without risk, especially given Trump’s erratic nature and polarised standing in US and international opinion. While seeking the potential upside in the new relationship, including the possibility of a trade deal, May would be wise not to overestimate the UK’s ability to shape US power, and be blind to the fact that Trump’s “America First” outlook may — ultimately — care little for UK interests.

Andrew Hammond is an associate at LSE IDEAS (the Centre for International Affairs, Diplomacy and Strategy) at the London School of Economics.