Individuals and private companies should take responsibility for preparing themselves for a terrorist attack, a security conference is to be told.
Emergency services in London practiced for a terror attack
A former head of Israeli intelligence service Mossad will say that governments, including Britain's, cannot be expected to protect everyone.
Efraim Halevy will also tell the London meeting that he is deeply concerned about Iran's nuclear programme.
Thursday's one-day event is aimed at bringing together experts in terrorism and security from both the British government and the private sector.
Mr Halevy, who spent four years running Mossad before he stepped down in 2002, spoke to the BBC about his concerns on the eve of the conference.
Whitehall officials, local authorities and others will hear him argue that the new age of terrorism has changed the way countries need to prepare themselves.
He said the public and businesses need to budget for how they would survive the effects of an attack.
Mr Halevy, who spent 38 years in Israeli secret intelligence and developed close working relations with several Arab governments, said he was particularly worried about Iran.
He also condemned Syria's conduct during the Iraq war, but said that confronting Saddam Hussein was the right thing to do.
Although no weapons of mass destruction have since been found, Mr Halevy said he had no doubt whatsoever that Saddam intended to manufacture such weapons.
He said the final story in Iraq has yet to be told.
Security firm Ozonelink, the company behind the conference, said it is intended to look at what the security issues facing the public and private sectors are.
The firm said that at present civilians "attach little credibility, see no relevance, or feel there is little they could do to prepare for the next 'event'".