[en] An overview of the development of CAGR on-load refuelling is presented from early experiences at Hinkley Point B and Hunterston B through the present phase of batch refuelling at low reactor power to the eventual aim of refuelling individual channels at high reactor power. The operational and economic incentives for the continued development of CAGR on-load refueling are presented. The principle elements of a refuelling safety case are described, together with a discussion of the refuelling power limitations which are imposed by the present design of fuel and plant. The potential for improvements, both in design and in the detail of the safety argument, are described with particular emphasis on the developments which are necessary to the eventual achievement of CAGR refuelling at or close to full power. (author)