The evidence-policy interface is important for delivery of sustainable development policy. We examine one specific form of knowledge brokering, the temporary placement of academic research scientists in UK policy arenas. We argue that successful knowledge brokerage depends on establishing social processes critical to effective knowledge exchange. Merely facilitating proximity of academic and policy actors is insufficient. Cultural understandings are key conditions for knowledge brokerage in this context. Academics who are outsiders to the policy process need to become credible insiders in order to be effective in bringing an outsiders' perspective into play.