Mrs Peel, we're needed.

No one else could have been (or will ever be) John Steed.

I think of the scene in "Mr. Teddy Bear" where Cathy throws him to the ground (twice). He's not going easy on her, he's not trying to be gentle with her because she's a woman - she's literally a better fighter than he is, and he recognizes that. Even his annoyance when he tries to kiss her and she slams him back is short-lived - he pushed it too far, and she said no, and he accepts that pretty quickly. Throughout her seasons, he openly respects her ability. There's never a point where he thinks that this makes him less masculine, or where he feels he needs to run her down or condescend to her.

Cathy: Goddammit, I'm going to sleep with him again, aren't I?

Ok, this has got to be my favourite discovery, after watching this episode for the gazillionth time. Look how close Diana puts her face to Patrick's face, as they act out Basil and Lola's exit. I mean, was that in the stage direction? Does she kiss him? Or nuzzle him, then rub her nose across his? I mean, look at him when she turns; he's absolutely delighted and his left hand is on her hip, which we can barely see, from the camera angle.

This happens on the periphery of the action, so I can't see it being relevant to the script; I can only assume it was them having fun and improvising. But who's that in sync with this level of intimacy, during improvisation, if you're just friends and colleagues.