The preliminary finding by Italian investigators that those who took part in the attempted bomb attacks on London on July 21 were probably unconnected to any larger terrorism network raises a fresh and intensifying concern for intelligence and security services world-wide: that there is a new breed of Islamic terrorism that has no link to old al-Qaeda structures.

According to western security officials, the topic of home-grown, radicalised Muslim extremists shifted near the top of counter-terrorism agendas more than a year ago during regular bilateral discussion between the the US and the UK’s homeland security services after a series of arrests of domestic terror suspects in both countries.