The problem we present is the object of the ROADEF Challenge 2016. It consists in an Inventory Routing Problem over a long time horizon with additional features: the objective function to minimize is fractional (cost per unit delivered); there is no prior assignment of drivers to trailers; the time is accurately modelled: non-constant hourly consumption of each customer is provided while minute-precise delivery planning needs to be determined; vehicles can perform multiple trips during the working day. The problem calls for the determination of a delivery planning that respects operational constraints and avoids customer stockouts.