THE world’s biggest banks, including Citi and Goldman Sachs, will draft in senior traders to work through the night following Britain’s referendum on European Union membership, set to be among the most volatile 24 hours for markets in a quarter of a century.

    A vote to leave the European Union next Thursday would spook investors by undermining post-World War Two attempts at European integration and placing a question mark over the future of Britain and its US$2.9 trillion economy.

    Citi, Deutsche Bank, JPMorgan, Goldman Sachs, HSBC, Barclays, Royal Bank of Scotland and Lloyds are among those banks planning to have senior staff and traders working or on call in London as results start to dribble in after polls close at 2100 GMT, according to the sources.

    Jamie Dimon, chief executive officer of JPMorgan Chase & Co., told employees on a visit to Britain this month that if the vote was to leave the European Union, the bank would have to have “teams of people thrown on what that means.”

    “We won’t know what it means: there is a wide range of outcomes,” said Dimon, a supporter of Britain’s membership who has warned of job cuts at JPMorgan in Britain if there is an “out” vote.

    A vote to leave could unleash turmoil on foreign exchange, equity and bond markets, spoiling bets across asset classes and potentially testing the infrastructure of Western markets such as computer systems, stock exchanges and clearing houses.

    Federal Reserve Chair Janet Yellen has cautioned that a Brexit vote could shake financial markets and potentially push back the timing of the next rise in U.S. interest rates.

    Bank of England Governor Mark Carney has said sterling could depreciate, “perhaps sharply” and some major banks have forecast an unprecedented fall to parity with the euro and as low as US$1.20 in the days following any vote to leave the bloc.

    The Bank of England will be staffed overnight, with senior policymakers on call if markets go into meltdown. The finance ministry would not comment on its staffing plans.

    The official Vote Leave campaign argues there is no evidence that leaving the EU would weaken sterling long term, while Nigel Farage, leader of the U.K. Independence Party, has said that even if the currency did fall, it would simply boost British exports.

    Sterling, the world’s fourth-most traded currency, has moved sharply in recent weeks, often on the back of opinion polls.

    Depending on the results from across the United Kingdom, the night of June 23 and early morning of June 24 could rank as one of the most volatile nights in the history of the London market.

    “We’ve all seen U.S. elections, U.K. general elections, we’ve had the Scottish referendum, the collapse of Lehman and QE [Quantitative Easing] but this is by far and away the biggest risk event that has presented itself to the U.K.,” said Chris Huddleston, head of money markets at specialist bank Investec.

    London accounts for 41 percent of global turnover in the US$5.3 trillion-a-day foreign exchange market, more than double the turnover in the United States and far more than the 3 percent of its closest EU competitors, France and Switzerland. (SD-Agencies)