BRUSSELS: A Swedish citizen working for the European Union diplomatic corps has been imprisoned in Iran for more than 500 days, making him an important bargaining chip for Tehran as it tries to wring concessions from the West. The arrest, which has been kept under wraps for over a year by Swedish and EU authorities, appears to be part of an expanding pattern of what has become known as Iran's "hostage diplomacy." Tehran has been opportunistically scooping up dual Iranian nationals and foreigners on spurious charges, seeking to...