Britain facing a 'new reality' as fears grow attacks are inspiring copycats
Britain has been hit by an "unprecedented" wave of terror attacks and one atrocity may be triggering the next, London's top police officer has warned.
Scotland Yard chief Cressida Dick said authorities were confronting a "new reality" after three deadly assaults in 10 weeks.
In the latest outrage, three terrorists killed seven people and injured dozens more in the London Bridge area on Saturday.
The incident followed murderous strikes in Westminster and Manchester in March and last month respectively, and Ms Dick, whose policing career spans more than 30 years, said the flurry of attacks was "unprecedented in my working life".
Islamic State (IS) has claimed responsibility for the London Bridge rampage, while the attack has sparked fears that Britain is in the grip of a spate of copycat incidents.
Ms Dick said it was "certainly a possibility" that the attacks were triggering the next one.
"The rhetoric that has been coming from IS and other organisations has been to encourage people to take action into their own hands, to use low-tech methods," she said.
"Undoubtedly, when people see something which appears from their perverted point of view to be successful, some people will be inspired by that, so that is most certainly a possibility."
Counter-terrorism police and security services have launched a huge investigation for the third time in a matter of weeks.
Assistant Commissioner Mark Rowley urged anyone with information about the latest attack to come forward.
"The police and our partners are doing everything we can across the country to help prevent further attacks and protect the public from harm," he said.
"At any one time, MI5 and police are conducting around 500 active investigations involving 3,000 subjects of interest.
"Additionally, there are around 20,000 individuals who are former subjects of interest, whose risk remains subject to review by MI5 and its partners.
"The security and intelligence services and police have stopped 18 plots since 2013, including five since the Westminster attack two months ago."
Meanwhile, large concrete barriers have been installed at Waterloo, Lambeth and Westminster bridges in London.
Police have also been guarding the capital's main bridges in order to stave off any potential copycat attacks.