World leaders gathering in Britain ahead of the funeral of the late sovereign lady, Elizabeth II, at London’s Westminster Abbey on Monday, will experience a country in national mourning — and Britain’s new prime minister, Liz Truss, will likely be the most visible among them.

While Ms. Truss arrived at Number 10 Downing Street only on September 6 and has not even finished naming all her ministers, the new premier will fly to New York City on Monday night just hours after the funeral and ahead of a speech she will deliver to the United Nations General Assembly.

Government activity in Britain has for the most part ceased since September 9, the day after the death of the monarch, and the Truss cabinet will not resume its normal course until Tuesday, the day after the funeral. Ms. Truss, though, has not been invisible in this period, having made trips to Edinburgh in Scotland, Belfast in Northern Ireland, and Cardiff in Wales, all to attend services in memory of the Queen.

The sweep of events since assuming office may have put on hold any semblance of a normal agenda, but the time will come soon enough for brass tacks on Britain’s energy and cost-of-living crises. The trip to New York for her first overseas meeting as prime minister will be the first opportunity for Ms. Truss to burnish her credentials on the international stage. 

The Times of London reports that Ms. Truss will “be packing two weeks’ worth of announcements into four days before parliament breaks for the conference recess.” No wonder, after six weeks of the Conservative party primary period, during which her predecessor Boris Johnson was only intermittently in Britain, followed by the death of and mourning for the Queen. 

The bilateral meeting that the Times of London reported Ms. Truss was set to have with President Biden in Britain on Sunday, before the state funeral for the Queen on Monday, has been called off, but the New York Post reported that the meeting with the Mr. Biden will now take place at New York on September 21, when both are set to attend the General Assembly.

The speech Ms. Truss is due to give could be a newsworthy one. The Telegraph reports that she will be expected to make the case that greater economic growth in countries such as Britain will help the free world take on authoritarian regimes and bring down the cost of living.

The speech is likely also to “include a rallying call for nations to help Ukraine in its pushback against Russian forces” and is expected “to champion Ms. Truss’s approach in the UK of reducing the country’s reliance on imports from malign states.”

Many watching from Britain will likely  focus more on Ms. Truss’s style than the substance of her remarks. That is because, while already branded as “Ruthless Liz” by the London Times, Ms. Truss herself has admitted that she is not the world’s greatest public speaker. 

As foreign secretary under Mr. Johnson, she displayed plenty of political acumen but lacked the effortless verbal sparkle of her predecessor. New York Magazine went so far as to criticize Ms. Truss as being “so far, a Margaret Thatcher impersonator with a lively Instagram account and a relationship to authenticity as addled as Johnson’s own.” There is arguably no better city in the world than New York for Ms. Truss to prove her detractors wrong.