Swarm robotics has the potential to radically change the economies of size in agriculture and this will impact farm size and structure in the UK. This study uses a systematic review of the economics of agricultural robotics literature, data from the Hands Free Hectare (HFH) demonstration project which showed the technical feasibility of robotic grain production, and farm-level linear programming (LP) to estimate changes in the average cost curve for wheat and oilseed rape from swarm robotics. The study shows that robotic grain production is technically and economically feasible. A preliminary analysis suggests that robotic production allows medium size farms to approach minimum per unit production cost levels and that the UK costs of production can compete with imported grain. The ability to achieve minimum production costs at relatively small farm size means that the pressure to “get big or get out” will diminish. Costs of production that are internationally competitive will mean reduced need for government subsidies and greater independence for farmers. The ability of swarm robotics to achieve minimum production costs even on small, irregularly shaped fields will reduce pressure to tear out hedges, cut infield trees and enlarge fields.