Craigs Investment Partners broker Chris Timms said yesterday Mrs May was due to trigger Brexit - whereby the United Kingdom starts the process to leave the European Union - on Wednesday UK time.
``This will start the clock ticking on the two-year timeframe Britain has to exit which will need to be complete by the end of March 2019.''
A European Union summit on Brexit is to be held in a month but it could take several weeks for the other 27 countries to start the formal process, he said.
It remained to be seen how Brexit would ultimately affect the British economy. Some indicators, such as the latest performance in manufacturing index surveys, indicated activity levels had lost steam. Others, like last week's retail sales data for February, were looking surprisingly strong.
In the United States, markets moved lower on Friday and major indices posted their largest weekly losses in months as caution set in ahead of the healthcare Bill vote, Mr Timms said.
The Bill was withdrawn over fears it would fail, raising concerns that despite the Republicans having the majority in both houses and the presidency, they might be unable to agree on policy.
``This has put doubt in investor minds the proposed tax reforms and stimulus packages will actually be able to be put in place.''
The White House warned rebellious conservative politicians they should get behind Mr Trump's agenda or he might bypass them on future legislative fights, including tax reform.
The threat by White House chief of staff Reince Priebus to build a broad coalition on tax reform that could include moderate Democrats came as the Republican head of the tax-writing committee in the House of Representatives said he hoped to move a tax Bill through his panel soon.
Mr Timms said there were only four trading days to go in the March quarter and it was shaping up as a ``pretty decent one'' for New Zealand investors.
The local market was up 2.8% so far this quarter, a much better performance from the 6.5% fall in the three months ended December - the worst quarter since 2010.
All the major global equity markets had also risen, and the US was one of the better performers. The S&P 500 had gained 4.7% so far this quarter - the best performance since 2015.
The New Zealand dollar was up slightly against the US dollar although returns from US shares still looked solid despite that move. A weaker New Zealand dollar against the Australian currency and euro had boosted returns in all those regions. The currency was flat against the pound in the year to date.
In the US, technology had been the star performing sector with a rise of nearly 11%. Energy had been the weak link, falling 8.9%.
Healthcare topped the list in Australia with an 11.9% gain and telcos were down 8.9%.
The best NZX50 stock so far this quarter was The a2 Milk Company, up 32.9%, followed by Ebos (12%) and Auckland Airport (11.9%).
Metro Performance Glass (down 23.1%), Fletcher Building (down 23%) and Tegel (down 18.7%) were at the other end of the spectrum, Mr Timms said.
Tomorrow, milk company Synlait is due to report its first-half financial year, followed by Hallenstein Glasson on Thursday. The Tower annual meeting will also be held on Thursday.
