20 years after London's deadliest bombings, extremist threat grows more complex

Twenty years ago today, four coordinated bombings tore through London's transport network, killing 52 people and injuring hundreds. The four perpetrators who died in the blasts were all raised in the UK, and were later revealed to have been motivated by Islamist extremism. In the years since, British security services say they've become far better equipped to detect and prevent such attacks. But as The World's Europe Correspondent Orla Barry reports, the nature of the threat is more complex than ever.