British Prime Minister Theresa May today attends her first European Union summit since she came to power in July in the wake of her country's decision to leave the EU.

While Brexit does not formally feature on the summit's agenda, it will be the main topic of discussion over dinner tonight, when Mrs May is expected to outline her strategy for conducting the separation negotiations. EU leaders are bracing themselves for an unconvincing message from a British leader who is struggling to prevent her own government from splitting on the issue.

Soon after Britons voted by a narrow majority to leave the EU, the assumption in European capitals was that the United Kingdom would take a long time to form a new government but, once formed, that government would seek to maintain as many links as possible with Europe by opting for a so-called "soft Brexit".

In reality, precisely the reverse happened. Mrs May's ascent to power proved to be relatively swift, while her negotiating stance with Europe appears to be hardening by the day. When she formed her government, Mrs May vowed to avoid "giving a running commentary" on her negotiating stance. With every speech she has made since then, however, Mrs May has given the impression that she is opting for a "hard Brexit", in which Britain's relations with Europe are largely severed, to be replaced by newly negotiated special deals.

The main area of controversy is border controls, where Mrs May's government insists that while it wants to retain Britain's access to European trade markets, it wishes to reimpose controls on EU citizens coming into the UK. That infuriates European leaders, who insist that the EU is a single entity which includes free movement of both goods and people, and that the two won't be separated.

Mrs May's stance has also alienated EU president Donald Tusk, hitherto sympathetic to British interests, who recently warned London that cherry-picking between European obligations and benefits is "pure illusion" and that Britain must expect to suffer for leaving the EU. "In my opinion, the only real alternative to a hard Brexit is no Brexit," he said.

Mrs May will use today's summit to reassure EU leaders, many of whom she has not met before, that despite the threatening noises coming out of London, she retains an open mind about the shape of Britain's future links with Europe. She has already made one small concession, by announcing that Britain intends to formally start Brexit negotiations by next March.

She will also point out that although the British government insists on the imposition of some border controls as the country departs from the EU, London is careful not to spell out what these may be, so there is still plenty of room for manoeuvre. One possible compromise which she may tout is the possibility of imposing caps on the number of EU citizens entering the UK after Brexit, or introducing safeguards to protect Britain from sudden surges in EU citizens coming to work.

Neither of these approaches is attractive to other European governments. Still, EU leaders are encouraged by indications that Mrs May and her ministers are at long last confronting the practical implications of Brexit.

A paper circulated earlier this week to the British Cabinet warned that pulling out of Europe's single market could lead to a 4.5 per cent fall in British gross domestic product. The British Treasury has also estimated that, after withdrawal from the bloc, Britain would need to increase its trade with countries outside the EU by at least 37 per cent by 2030 just to compensate for the anticipated loss of trade with Europe.

The enormity of both figures is testimony to the real challenges facing the UK.

Yet, what European leaders will be looking for most during today's dinner discussions is clarification on where MrsMay herself stands on these questions, and what her own views on Europe really are.

All EU capitals are aware that the British government is currently being torn apart by disputes between anti-European ministers such as Foreign Secretary Boris Johnson and pro-Europeans such as Finance Minister Philip Hammond, but they don't know where the British premier stands, or how she will react if these divisions within her Cabinet become worse.

Mrs May will have to persuade her European colleagues that she has a clear vision of Britain's place in the continent, and that she intends to pursue this vision regardless of the obstacles.

For clarity is now the commodity Britain lacks most.