The word 'diaspora' has leapt from its previously confined use - mainly concerned with the dispersion of Jews, Greeks, Armenians and Africans away from their natal homelands - to cover the cases of many other ethnic groups, nationalities and religions. But this 'horizontal' scattering of the word to cover the mobility of many groups to many destinations, has been paralleled also by 'vertical' leaps, with the word diaspora being deployed to cover...