Political Unknowns Lurk for U.K. Risking Favor With Markets

Political danger is looming for Britain, threatening to dim the allure of the fastest-growing Group of Seven economy.

An election in less than 10 months could clear the way for Britain to leave the European Union, its biggest trading partner, if David Cameron remains prime minister. In September, Scotland votes in an independence referendum that threatens to rend the U.K. asunder. All this comes amid warnings that possible further sanctions against Russia over Ukraine might hurt the U.K. economy.