Back in 1993 and 2000, Lang and LeCocq, respectively, in their reactions against reductive and de-contextualised forms of "source work", pointed out that all sources do hold value in some way, even, and often especially, in those aspects that might be deemed "biased". The author's Year 10s' difficulty in shaking off a certain kind of "bias" obsession worried him, both in terms of their performance in an examination that requires judgement on sources and, more profoundly, in the consequences for the quality of their historical thinking. The author had decided that the time had come to take action. He had three main objectives for his anti-bias battle. First, he wanted to use an interesting story and intriguing source to ensure high engagement, drawing students more deeply into the "world" of the First World War. Second, he intended to further develop my pupils' ability to infer and to evaluate. Third, and crucially, he aimed to force the group to stop seeing sources in black and white, that is, "biased" or "not biased", and to stop seeing some neat but false correlation between this and the source's utility. The author decided to carry out a one-lesson enquiry into "What can Philip Gibbs tell us about the First World War?" The lesson began with Gibbs' life story up until 1916. The lesson was brought full circle with an outline of the rest of Gibbs' life story, including a short reading from Gibbs' post-war book, "The Realities of War" as a contrast to our other source. The lesson is decribed in this article.