21/7 bombs 'not meant to explode'

From the beeb:

"The man accused of making bombs to attack London's transport network on 21 July 2005 did not intend to hurt anyone, a jury has heard.

Muktar Ibrahim, 29, conducted tests on hydrogen peroxide and chapatti flour mixtures to ensure they would only go "pop", Woolwich Crown Court was told."

Designed to go pop, were they? Ok - good luck with that line of defence.