(Bloomberg) -- Currency traders are taking no chances as the U.K. Parliament’s Brexit vote late Tuesday will come during thin liquidity heading into the market’s witching hour.

Money managers are canceling evening plans to stay at the office to ensure they don’t miss market swings like those seen during sterling’s 2016 flash crash or the chaos that followed the Swiss National Bank unexpectedly dropping its currency floor in 2015. The pound could move as much as 6 percent in either direction depending on the vote’s outcome, strategists say.

“That’s one of the SNB lessons learned, there were a lot of less experienced people on the desk,” said Alan Schwarz, New Jersey-based CEO of FXSpotStream LLC, a trading venue launched by banks. “I will guarantee you a lot of the most senior people at the banks will be at their desk or will be able to get to it.”

With the memory of the 2016 plunge in the pound provoked by thin liquidity in Asian hours still on their minds, traders will be hoping the vote doesn’t come too late. The result is due around 8:30 p.m. U.K. time, but a delay could see it pushed between the end of the New York close and the start of trading in Tokyo.

A relatively small shortfall in the votes Prime Minister Theresa May needs to pass her deal could actually spur gains in the currency on the prospect of talks for a second attempt, according to strategists. A large loss ignites risks including a no-confidence vote, a push for a second referendum or an election, which would drive sterling lower. Options betting on one-week volatility are holding near an 18-month high.

A late-running vote wouldn’t just see investors trapped at their desks, but could exaggerate any moves in the pound due to the thin liquidity. According to 2016 data from consultancy Aite Group, foreign-exchange volumes dwindle to just 2 percent of peak turnover between the New York close and the start of trading in Tokyo.

Liquidity is much more of a concern than it used to be, said Andreas Koenig, head of global currencies at Amundi Asset Management. It wasn’t even a topic of discussion when he started in the market in 1994, but the “erratic nature of liquidity” means it’s now something to bear in mind, he said.

Global Operation

In Europe, Commerzbank AG strategist Esther Reichelt said she has cleared her evening schedule and has several colleagues who simply don’t want to miss it. Swissquote Group Holding SA is making extra staff available, according to its head of forex, Ryan Nettles.

In the U.S., FXSpotStream’s Schwarz has told his wife to make her own way home that evening, hears banks have beefed up staffing, and has a message for his own team: “Don’t make plans to be anywhere else but here.” In case the vote runs beyond the end of the U.S. trading day, he plans to sleep at the home of another colleague who lives near the office.

Asian trading desks may opt to start their day early, said Schwarz. While firms including Swissquote confirmed they would be staffing the evening from Europe, some banks are saving their resources for what could be an explosive session in Parliament the day after the vote, according to several traders who spoke on condition of anonymity.

The most unexpected outcome would be May winning.

“If it does pass, we’ll all go ‘Oh, my god!’” said Norman Villamin, chief investment officer at Union Bancaire Privee Ubp SA.

A shock 320-vote majority for May could lead the pound to rally more than 6 percent from around $1.27 now to $1.35 for Mizuho Bank Ltd. If May loses as expected, traders will be watching the margin of votes for hints on what happens next. Barclays Bank Plc predicts a rejection by more than 75 votes would see the pound plunge to $1.20, a level that could turn up the heat on lawmakers to avoid the U.K. crashing out of the bloc in March.

“The vote could be construed as more important than an election in terms of pound implications,” said Neil Jones, head of currency hedge fund sales at Mizuho. “Depending on the outcome, cable could move more than through an election result.”

To contact the reporters on this story: Charlotte Ryan in London at cryan147@bloomberg.net;Shoko Oda in London at soda13@bloomberg.net

To contact the editors responsible for this story: Ven Ram at vram1@bloomberg.net, Neil Chatterjee

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