This troubles me, because you have glossed over this as though there is no real reason for such a thing. At borders there is often preferential treatment given to people based on certain characteristics like where they were born or what their passport says. I wouldn't like to speculate what may have ensured a white British female academic moved quickly through the barricade, whilst Arabic appearing men and women were kept waiting a little longer. As an interim answer, I'm going to say 'security concerns' - possibly due to the Hamas response to the Oslo Accords and the subsequent election of Hamas in 2006. It isn't nice, but it is fathomable.