Based on insurers' trade associations' archives, this paper highlights the strategies developed by life insurers vis-à-vis the expansion of state old age provision in postwar Great Britain and Switzerland. In these two countries, group pensions managed by private insurance companies have constituted a significant share of occupational old age provision since the interwar period. Accordingly, Swiss and British insurers lobbied to shape multi-tiered pension systems that would safeguard the market for private provision. However, the outcomes of these postwar pension debates were quite different: whereas British insurers developed early on the idea of "contracting out" occupational provision as a response to Labour's proposals for earnings-related pensions (1958-1970s), Swiss insurers fought for the introduction of a mandatory "second pillar" of pension provision (1968-1985). Contrasting these strategies and outcomes enables us to better understand the role of a key business constituency in social policy debates.