In offering a contribution to a session concerned with ‘the background to Lyell's work’, I want to begin by launching a caveat against the notion of ‘background’. If, in the case of Lyell, ‘background’ features remained in obscurity then they can be dismissed; if, however, ‘background’ features were important then they become foreground. This point is not merely linguistic pedantry, because if we look at the scientific institutions of London in the period 1820–41, it is too easy to assume, with naïve optimism, that if they existed they must have been functionally effective for scientists. This was not necessarily so. We have to discover, as a matter of contingent reality, the ways in which particular institutions actually affected the careers of individual scientists. In this paper, therefore, I shall offer some general observations on London scientific institutions; and then I shall analyse Lyell's varying allegiances to them in terms of his ambitions concerning the shape and direction of his career.