China’s Mao-era science diplomacy involved strategies and structures that underpinned the hosting of foreign visitors such as scientists. Chapter 5 focuses on networks of individual relationships – professional, personal, and political – that ran through Chinese involvement in the organisations and events discussed in this book, focusing on some of those that developed between Chinese and left-wing British scientists from the 1940s through to the 1970s. Considering the experiences of J. D. Bernal, Howard E. Hinton, Dorothy Hodgkin, Kathleen Lonsdale, and Kurt Mendelssohn, it elucidates the range of motivations, responses, and outcomes on either side of scientists’ visits to China as part of everything from ‘friendship’ delegations made up of political sympathisers to lecture tours organised by scientific organisations. These British scientists had much in common with many other sympathetic visitors from the time, at least in broad strokes; nevertheless, this chapter identifies several key characteristics that set such scientists apart as a category of foreign visitor during the Mao era.