LONDON — Prime Minister Theresa May, who has for many weeks evaded debate over how Britain will exit from the European Union with the phrase “Brexit means Brexit,” promises more clarity in a speech later this month.

She is expected to speak two months before she intends to invoke Article 50 of the Lisbon Treaty, formally beginning a two-year negotiation with Brussels on leaving the European Union, and just after the Supreme Court rules on whether Parliament must approve that invocation.

The Supreme Court, the United Kingdom’s highest court of appeal in civil cases, is expected to rule against the government and require that Parliament have a say. A short bill has already been prepared, however, and no one expects lawmakers of either house to oppose the result of the June “Brexit” referendum at this stage.

So Mrs. May will speak. But what will she say, especially when she insists that she does not want to give away her bargaining position with Brussels too early? And how will she calm down the fervid, angry and partisan atmosphere around the whole topic — both in the country at large and, more important, in her own Conservative government?