Mistrust of experts is part of the modern zeitgeist - as demonstrated in the run-up to the UK's EU Referendum vote in June 2016 and the US Presidential Election in November 2016. Is it right to question experts' objectivity and impartiality and challenge their roles in the formulation of policy? Traditionally, we tend to believe that experts are offering impartial and unbiased advice, based around an objective assessment of evidence and the careful application of robust research methodologies. In practice, however, a range of behavioural biases and social influences, as well as opportunistic behaviours, have the potential to distort expert judgements. This paper will explore some of the economic, social and psychological influences that might distort the provision of objective advice to policy-makers. It will explore some of the ways in which socially driven bias can distort the evolution of knowledge and explore some policy implications, including ways to ensure that expert advice is devised and applied in the most robust and objective ways possible.