This is a nicely composed shot - one of many in this enjoyable story. Look, there's General Veers from The Empire Strikes Back, pretending to be Richard the Lionheart.
The story seems to be largely about people trying to have sex with each other. Though, this being Doctor Who, no-one actually comes out and says anything. They all pretend it's about honour, or something. But it's definitely about sex.
Barbara's having none of it, though. I've seen that look. He's no chance.