Whitehall officials have told the BBC that contrary to recent announcements, the number of Britons emigrating to Syria to live under Islamic State (IS) rule peaked two years ago. However, the proportion of women among those joining the extremist group has risen dramatically. So what’s behind this and what exactly is the IS strategy behind luring women into their ranks? Our Security Correspondent Frank Gardner investigates.

Islamic State, also known as Isis, has a dual attitude to women.

On the one hand it treats those it considers heretics as almost sub-human, as commodities to be traded and given away as rewards to jihadist fighters.

Shocking footage from a modern-day sex-slave market in Mosul, Iraq, shows militants discussing prices for Yazidi girls, captured last year, many of them underage.

At least 2,000 Yazidi women are still being held, only a few have escaped.

‘Corner stones’

“They put us up for sale,” said one who did recently escape. “Many groups of fighters came to buy. Whatever we did, crying, begging, made no difference.”

But on the other hand, IS has big plans for Muslim women […]