The man initially failed to stop for police officers when indicated to do so, and in the process of trying to evade officers, drove the bike in a dangerous manner, until he lost control of the bike and fell off it. He was arrested for failing to stop, dangerous driving, driving without a licence and insurance, and suspicion of theft of motor vehicle.
The Sur Ron bike the man was riding is illegal for use on the UK Public Highway, due to having an electric motor of above 250 watts and a top speed of over 15.5mph. If you are considering buying an electric bike for use on the roads in the UK, be sure to check on the legalities first and especially that the bike you are considering buying complies with the 250watt and 15.5mph restriction.
You can find the legislation applying to electric bikes at the https://crowd.in/uY8ve7 page here: