The authors historically situate the London Kleinian development in terms of the small-group collaborations and adversaries that arose during the course of Melanie Klein's career. Some collaborations later became personally adversarial (e.g., those Klein had with Glover and Schmideberg); other adversarial relationships forever remained that way (with A. Freud); while still other long-term collaborations became theoretically contentious (such as with Winnicott and Heimann). After the Controversial Discussions in 1944, Klein marginalized one group of supporters (Heimann, Winnicott, and Riviere) in favor of another group (Rosenfeld, Segal, and Bion). After Klein's death in 1960, Bion maintained loyalty to Klein's ideas while quietly distancing his work from the London Klein group, immigrating to the United States in 1968.