In a move taken by few other nations, it [new law] requires telecommunications companies to store for a year the web histories known as internet connection records — a list of websites each person has visited and the apps and messaging services they used, though not the individual pages they looked at or the messages they sent.

Source: Sweeping UK spy bill dubbed ‘snoopers’ charter’ becomes law – SFGate

No warrant is required to access the data and the list of accessed web sites will be available to nearly any government agency, not just police investigating crimes.

This is the largest, publicly disclosed, mass surveillance system in history.

Coldstreams