Dr Thomas Dixon continues to trace the changing meaning of friendship over the last five hundred years. Episode 13: In Need, In Deed, By Post Mass Observation and the archive of the Co-Operative Correspondence Club provide intimate evidence for friendship during the Second World War. Dr Clare Langhamer discusses how, in 1935, one lonely mother in County Wicklow began a correspondence network that continued through to the 1990s, long preceding today's MumsNet and NetMums. She also shares some revealing evidence from the vast Mass Observation archive at the University of Sussex about how women's friendships were affected by their war-work. Thomas Dixon also considers how men on active service formed new bonds across the class divide, and, in one extraordinary case from the BBC Sound Archive, not only with other human beings: "I have a passion for tanks," begins Captain Michael Halstead's account of life on the front line. Producer: Beaty Rubens.