Well, it was the director's girlfriend - or maybe just a woman he wanted to shag? Memory fails. He was good enough - the finished piece looked fantastic - and I was doing a favour for a friend, so it was all OK. The girl had a list of London credits that I doubted heavily, but she came off very well on camera, so <shrug>. It's nowhere near my worst experience with a film actor, only annoying at the time, and totally worth it (as most things are) for the story.
From my understanding, the repetition exercise has always been something taught to brand-new students in the first month of acting classes, to demonstrate the difference between reciting lines and saying things in a spontaneous, believable manner. As well as to teach what subtext is.
The idea that anyone would be doing the repetition exercise after their first month of acting school baffles me. It's not a technique that was ever intended for, or should be used by, professional actors, as far as I've ever understood it.