British intelligence may have been leaked to Russia by an alleged German double-agent, an expert on Berlin’s spy services said. British spy chiefs are reportedly furious about the affair, which saw a senior figure inside Germany’s Federal Intelligence Service (BND) arrested shortly before Christmas. In one of the most spectacular double-agent scandals in decades, Carsten L, head of a division inside the BND’s signal intelligence wing, was arrested on charges of high treason in December. Germany believes that he was responsible for passing on highly sensitive battlefield information from the Ukraine war to the Russians. The case will likely have...