how do you set about conducting field research in an IS-controlled area?
"In the IS-controlled areas of Raqqa for each survey we visit the head of the town and ask him for permission to randomly interview people," Mr Heald says.
"His response is 'so long as you are not an international media station and pull out video cameras, I don't mind you doing this'."
"Why is this his reaction? Because, as the data verifies, many of those living in Raqqa now are happier since IS took over.
"They welcome the security, they see IS trying to help the people with electricity, with food, with petrol. In many respects it is a story they are keen to tell."