The National Physical Laboratory is the National Metrology Institute of the United Kingdom. NPL is the work-package leader for WP4, and participates in technical work-packages WP1, WP2, and WP3, based on its expertise in: developing traceable methods for characterising single-photon sources and detectors, and fibre-optics; coupling single-photon measurements to fibre-coupled high-bit-rate quantum key distribution components and modules; generating, manipulating and characterising photonic quantum entanglement.