The prospect of a terrorist attack taking place in Britain has been greatly exaggerated, UK risk managers were told last week.

Simon Sole, managing director of risk assessment group Exclusive Analysis, said: "Fears of a Sunni extremist terrorist attack using special weapons are greatly exaggerated. We are not looking at a scenario that includes mushroom clouds and massive casualties."

Sole, speaking at a Cila seminar on dealing with terrorism, also put into context worries about a ricin attack, after the publicity of an attempted attack in London by Islamic fundamentalist Kamel Bourgass.

"In aerosol form it [ricin] would require four tonnes to kill as many people as one kilogram of anthrax.

"And the probability of a terrorist group being able to mount an effective nerve gas attack is low. It is extremely difficult to disperse nerve agents rapidly in order to create mass casualties."