Unique Street Reference Number
The Unique Street Reference Number (USRN) is an eight-digit unique identifier (a geocode) for every street in the UK. == Responsible agencies == USRNs for England and Wales are published in the National Street Gazetteer (NSG) database, the authoritative source of information about streets in England and Wales. The NSG is managed by GeoPlace, a joint venture between the Local Government Association and Ordnance Survey (OS).
Source: Wikipedia — Unique Street Reference Number (CC BY-SA 4.0)