In the UK, only eBikes that comply with EAPC Regulations can be used on UK public roads without tax, insurance or registration. You can find out more about EAPC Regulations here: https://www.gov.uk/electric-bike-rules.
Bikes fitted with the 250w motor option This eBike has a motor with a continuous rated power output not exceeding 250w and speed assistance limited to 15.5mph. It meets EAPC Regulation requirements and can be ridden on public roads. Legally it is treated the same as any standard non electric bicycle. The only regulational difference is that the rider of the bike must be at least 14 years old.