Sonic weapons used on Thames during Olympics, says City Hall Tory

Conservative London Assembly member Tony Arbour used the Mayor's Question Time session at City Hall on Wednesday to ask Boris Johnson to consider the use of long-range acoustic devices (LRAD) as a cheaper alternative to water cannon for dispersing hostile crowds.

The Mayor interjected: "Is this some sort of April fool?"

Mr Arbour replied: "If it was an April fool why on earth was a substantial sum of public money invested in this during the Olympics to have sound cannon on barges outside this building and in the Olympic area?"

Mr Johnson continued: "I do not know what you are talking about.

"I'm going to have to find out about the sound cannon, if they existed and whether they are any use."