"We had sex on occasion," Stein said, answering the question Birkin hadn't really wanted to ask but obviously wanted the answer to anyway. "We were fighting partners and close...friends, for five years. He was my Weapon, and my favourite test subject. But when he found out I'd been experimenting on him in his sleep, he cut things off."

He shrugged, moving to the microscope to wait his turn to look at the tongue. "I don't think that's really that dickish, to be honest, but it is a shame."