An object handling system is described, the system having two substantially perpendicular sets of rails forming a grid above a workspace, the workspace having a plurality of stacked containers. The system includes a series of robotic load handling devices operating on the grid above the workspace, the load handling devices having a body mounted on wheels. The robotic devices can move around the grid under instruction from a computing device, the robotic devices being moved to a point on the grid above a stack of containers and then, using a lifting device, engage and lift a container from the stack. The container is then moved to a point where the objects in the container can be accessed. Modifications to the workspace and grid are described that allow vehicles and roll cages to be used to move stacks from the workspace to a point outside the workspace or from outside the workspace into the workspace.
