"Tens of billions" of pounds worth of investment is required to upgrade the UK’s transmission system as the generation mix decarbonises, a major study by National Grid Electricity System Operator (ESO) is set to conclude. Giving evidence to the Environmental Audit Committee’s ongoing inquiry into the security of energy supplies, the ESO's director of corporate affairs Jake Rigg noted the significant bottleneck between Scotland and England, with the former already host to a 35GW pipeline of offshore wind generation.