UK could curb migration if euro crisis worsens: PM LONDON (Reuters) - Britain could restrict immigration of Greeks and other migrants from euro zone countries affected by Europe's sovereign debt crisis in the event of "extraordinary stresses and strains," Prime Minister David Cameron said on Tuesday. "The legal position is that if there are extraordinary stresses and strains it is possible to take action to restrict migratory flows, but obviously we hope that doesn't happen," he said. "I would be prepared to do whatever it takes to keep our country safe, to keep our banking system strong, to keep our economy robust," he added. Current European Union rules allow the free flow of labour around member states. Reporting by Mohammed Abbas, Editing by Matt Falloon