London-based banks HSBC Holdings Plc and Standard Chartered Plc tumbled in Hong Kong after early results from Britain’s European Union referendum indicated greater support for an exit than academics had forecast. HSBC, which made about a third of its 2015 revenue in Europe, fell as much as 3.1 percent and Standard Chartered as much as 3.7 percent. Financial institutions including JPMorgan Chase & Co., HSBC and Deutsche Bank AG warned ahead of Britain’s vote that they could shift some operations from London if the U.K. left the EU. HSBC would probably move about 1,000 investment bankers to Paris in the...