On a sweltering afternoon last month, industry ministers and officials from no fewer than 18 of the 27 European Union countries piled into a Brussels conference room to discuss the future of Opel. The meeting showed every sign of being as heated as the temperature outside. Herman van Rompuy, Belgium’s prime minister, among other disgruntled delegates, demanded assurances that any rescue plan would not favour German plants of the European arm of the ailing General Motors above those in other countries.