Friends in my prep group had this. They were interviewed separately and asked about their childhood, lots of questions trying to guage what their experiences of attachment had been. I don't know any more than that but am seeing some of them at the weekend so can ask for further details if you like.
I thought I had a copy but that is for children's services which I imagine is different, a quick google uncovered the above link that may help. If not I suggest google scholar and type in attachment style interview. HTH