Volume III deals with the 'long twentieth century'. Its main themes are:
* the contraction of British industrial power and the shift to a service-based economy
* the decline of Victorianism and the rise of Modernism
* the climax of class society between the wars and the blurring of class lines after the 1960s
* the impact of two world wars
* the decline of British power and the empire
* the partition of Ireland
* the devolution of power to Wales and Scotland.