NHS England HTM 06-01 Electrical Services Supply and Distribution (2017 Edition) 5.9: Dual, diverse primary supplies where possible

For higher resilience, premises should where possible have two primary supplies (ideally each rated at 100%) with automatic or manual changeover, made diverse by coming from different DNO substations, preferably supplied from different parts of the grid, with separate cable routes into and around the site; for larger premises two separate HV feeders should be considered.