The author examines the evolution of Winnicott's theoretical differences with Melanie Klein and members of her group in light of recent publications and archival materials, namely the Collected Works of D.W. Winnicott and audio recordings of Winnicott's Los Angeles lecture on ‘The Kleinian Development’ in 1962 as well as John O. Wisdom's discussion of Bion's Learning from Experience in 1964. An argument is made that Winnicott was an ardent Kleinist enthusiast, (1935-1951) before he published his landmark ‘Transitional Object's paper in 1953. The author steers a middle path between a Winnicottian secondary literature that essentially distances his work from Klein's influence, and a Kleinian literature that essentially ignores his contributions. With the two versions of the ‘Transitional Objects’ papers in the context of newly published letters to members of the London Klein group, the aftermath of Winnicott's theoretical departure is examined. In his correspondence from 1951 to 1964, Winnicott grouped Kleinians into 3 sub-groups: 1) the ‘All-in’ Kleinians who maintained a strict adherence to Klein's theories; 2) the ‘Less-than-All-in’ Kleinians with whom Winnicott constructively dialogued, mainly by post; and 3) the ‘Promising’ Kleinians whom he hoped to influence. By 1964, Winnicott ended his entreaties to members of the Klein group.