Theresa May is to urge internet companies to take down extremist content being shared by terrorist groups within two hours, during a summit with the French president and the Italian prime minister.

May is meeting senior executives from Google, Facebook and Microsoft on the sidelines of the UN in New York on Wednesday alongside her French and Italian counterparts, Emmanuel Macron and Paul Gentiloni.
https://www.theguardian.com/uk-news/2017/sep/19/theresa-may-will-tell-internet-firms-to-tackle-extremist-content