Legislative socialisation has long been an important force for political deradicalisation in capitalist democracies worldwide. It remains barely explored, however, in large part because it is a process very difficult to track by conventional observational or survey methods. We circumvent these problems by taking advantage of an unusually propitious vote on televising the proceedings of the British House of Commons to chart the institutional deradicalisation of its Labour members. Socialisation effects are shown to be non-linear and, while the difference is not statistically significant, to be marginally stronger among Members of Parliament (MPs) with frontbench experience. The somewhat greater conservatism of frontbenchers, however, cannot be explained by anticipatory socialisation. Rather, it seems to be a function of doing well under 'rules of the parliamentary game' threatened by proposals for institutional reform.