The Government Says

Large Load Controllers: Tier 1 Cyber Assessment Framework and associated guidance

Large Load Controllers: Tier 1 Cyber Assessment Framework and associated guidance
Local copy of tier-1-load-control-consultation.pdf

https://www.gov.uk/government/consultations/large-load-controllers-tier-1-cyber-assessment-framework-and-associated-guidance

seen at 11:13, 23 June in Policy papers and consultations.