How do bright schoolgirls fall for jihadis? The same way they fall for Justin Bieber

How could they? How could girls brought up in the wealthy West abandon their families and their own bright futures to join Isis, a gang of vicious thugs? It’s not just our girls, either, they’re sneaking off to Syria from across Europe and America too, teenagers, bright ones typically, set on becoming sex slaves in a war zone.

London’s latest runaways — Shamima, Amira, Kadiza — were pupils at Bethnal Green Academy and the headmaster there, a Mr Keary, echoed most people’s reaction when he shook his head and said: ‘I don’t understand it. It doesn’t make sense.’

But Mr Keary’s wrong, most people are wrong. It does make sense. Let your outrage subside and it’s pitifully easy to see what draws these idiots to Islamism. It’s not evil, or any inherent flaw, but just a simple set of ordinary influences which combine to create catastrophe.

For a child to choose religious orthodoxy may seem sinister — aren’t teens supposed to want freedom? — but look again and it’s just the usual rebellion against a parent. These girls and others like them are usually second or third-generation Brits. Their parents have assimilated, hoped their children would follow suit, so they rebel by becoming Islamists. The Dutch academic Ian Buruma spotted the trend a decade ago in a book investigating the assassination (by an Islamist) of the film-maker Theo van Gogh. He said: ‘The main perpetrators of violence in the name of religion in Europe are not, on the whole, the original guest workers or refugees… it is their children born in Europe who are vulnerable to a modern, violent, revolutionary creed.’