This article charts a history of everyday bodily interactions on the London tube. Through hundreds of passenger statements, gathered after the murder of Teresa Lubienska at Gloucester Road station in May 1957, it takes a cross-section of passenger behaviour in the 1950s while re-tracing the evolving relationship between the concept and practice of personal space as it responded to and shaped a century of material changes. It examines how the shift from private to public ownership and the problem of passenger impatience—the ever-increasing desire to rush—reshaped tube stations and cars, giving rise to indeterminate spaces in which passengers increasingly improvised to manage the potential touch of one another. Automated central doors, the increasing frequency and spaciousness of cars and the increasing necessity to straphang all compelled tacit agreements that made and remade subjective boundaries between passengers in every interaction, deferring the final establishment of those boundaries as a given ‘personal space’. Through tracing these changes, this article rethinks narratives of modernity and governmentality. If tube travel represented what it meant to be modern, this was not an established, self-regulating anomie. The tube’s modernity was a condition of un-decidability in which the ‘final’ fixing of the self’s boundaries was contingent on intrinsically indeterminate spatial relations with others: a need, since the 1920s, to mind the gap.