In 1933, the celebrated German economist Robert Kuczynski and his wife Berta arrived in Britain as refugees from Nazism, followed shortly afterwards by their six children. Ju]rgen, known to be a leading Communist, was an object of considerable concern to MI5. Ursula, codenamed Sonya, was a colonel in Russia's Red Army who had spied on the Japanese in Manchuria, while MI5 also kept extensive files on her four sisters, Brigitte, Barbara, Sabine and...