Chancellor Angela Merkel has warned British Prime Minister David Cameron he is approaching a “point of no return” with the European Union over his immigration proposals, according to a report on Sunday said. News weekly Der Spiegel writes in its latest edition that Merkel told Cameron on the sidelines of an EU summit last month that his moves to limit an influx of EU migrant workers undermined core principles of the bloc. If he continues, Germany would no longer fight to keep Britain in the EU. …