With the clock now ticking on Brexit talks, analysts expected the U.K. would face an economic slowdown, stagflation and corporate defections.
Sarah Hewin, chief economist for Europe at Standard Chartered Bank, told CNBC's "The Rundown" on Thursday that investors' main concern was the lack of clarity on negotiations and whether there would be an agreement with the European Union by April 2019.
On Wednesday, the U.K. triggered Article 50 of the Treaty of Lisbon, which began the formal two-year process of Britain's departure from the EU.
"The EU is the U.K.'s most important trading partner. If we can continue to get some access to the single market that's going to be very important for a lot of businesses that have invested in the U.K. with a view really to having access to the EU market," she said. "It's unlikely that we're going to get a trade deal done in two years' time."
Hewin added that many companies doing business in the U.K. were unlikely to wait the full two years before deciding whether the pull the plug on some or all of their operations there.