The alleged arrest has not, as the story claims, been confirmed by the BBC. London Police Chief Lyndon Edwards doesn't actually exist. And Banksy's supposed real name, "Paul Horner," is very common in fabricated news stories.
Not only was "Horner" mentioned in previous Banksy hoaxes, but the International Business Times points out he was also cited as a Facebook executive in the famous story about Facebook introducing a fee to use the site, and named as the kid sentenced to 25 years for calling in a SWAT team on his video game opponent. Neither of those stories turned out to be true.
More than 200,000 people have shared the "news" on social media. Ignore them.