The warning came after 'The Sunday Times' quoted a senior intelligence source saying four active terror plots are under investigation
Scotland Yard warned yesterday that a terror attack in the UK is a case of "when" rather than "if" and the current threat level of "severe" in the country meant an attack was imminent.
"I feel and understand that fear, and as the police officer in charge of preventing such an attack I know you want me to reassure you. I am afraid I cannot do that entirely. Our threat level has been at "severe" for two years. It remains there. It means an attack is highly likely; you could say it is a case of when, not if," Sir Bernard Hogan-Howe, the chief of Metropolitan Police said.
The warning by Britain's top police chief came as 'The Sunday Times' quoted a senior intelligence source as saying that at least four active terror plots in Britain are being investigated by police and security services.
"There's four or five cases where there is a sense of a plot, where they are planning and plotting and intending to commit an act of terrorism rather than just being extremists," the source told the newspaper.
Last week Ben Wallace, the UK's new security minister, held talks with retail bosses and operators of sporting venues to review security at stadiums and shopping centres.
"In light of events in Germany and France, the government is keen to ensure that shopping centres and sports stadiums where there are large crowds are getting the support they require," said Wallace.
Another intelligence source said that Islamic State militants were increasingly going after "softer targets", as well as seeking to recruit people with mental health problems.
"Unbalanced people, mentally ill people, people with particularly violent or anti-societal or sociopathic tendencies are being recruited as foot soldiers; and then that is playing itself out in the most innocent and unassuming targets, such as the street crowds on Bastille Day in Nice," the source said.
A current review by the UK's National Police Chiefs' Council is expected to redeploy firearms officers from rural areas of the UK to major cities deemed to be at greater threat of terrorism.
The review, which started in March when Theresa May was home secretary and is now being overseen by her successor Amber Rudd, is expected to report in October.