UK hospitals have been criticized for fuelling obesity by allowing contracts with food retailers selling high fat and high-sugar products on hospital premises.We assessed the impact for a major retailer of increasing healthy food choices at their Royal Free London NHS Foundation Trust outlet. To assess the impact on sales, profit and acceptability to customers, a multi-component intervention based on behavioural insights theory was enacted over 2 months (November-December 2014) at the Royal Free site WHSmith. Sales data on all food and drink were assessed over three time periods: (i) 2 months immediately prior to, and (ii) immediately after the intervention, and (iii) the equivalent period 10 months later. Acceptability to customers was assessed via questionnaires, and profit assessed as a proxy for retailer satisfaction.Compared to the pre-intervention period, total sales increased immediately after the intervention, and again 10 months after the intervention. Sales of healthier options increased as a proportion of total sales following the intervention, sales of sweets and chocolates decreased, while the relative sales of other items remained similar.We demonstrated that healthier alternatives could be provided in a hospital retail premises without negatively affecting total sales, retailer or customer satisfaction.