Almost simultaneously, at the turn of the 21st century, Germany and Britain experienced the deepest crisis of their respective pension systems since the Second World War. In both cases, policymakers responded with far-reaching reforms. In both the United Kingdom and the Federal Republic, the political debate was dominated by the idea that demographic ageing was responsible for the pension crisis. The demand for greater intergenerational equality became the central legitimising formula for justifying fundamental pension reforms. However, a comparative historical analysis shows that a one-dimensional explanation of the pension crisis around 2000, based on the argument of demographic ageing, is not convincing. What was far more important than the demographic threat scenario for the crisis-like development of pension provisions was a combination of other factors that differed in Britain and Germany. For the United Kingdom, these include in particular the decline of the basic state pension and the accompanying increase in the importance of a poverty-based principle in old-age provision and the decline of occupational pension provision in its traditional form. In Germany, on the other hand, the rising unemployment rate, the targeted early retirement of millions of East German workers and the costs of German unification, which were largely borne by the social security system, were mainly responsible for the financial problems of the pension insurance system. In addition, the rising pension insurance contributions were identified as a central cause of the loss of German competitiveness in the debate on Germany as an economic centre, which was taking place at the same time. In both countries, the politically responsible actors were eager to take up the explanation pattern of demographic ageing because it allowed interventions in the pension system to be perceived as necessary consequences of a quasi-natural process and distracted attention from self-generated socio-political problems.