R427 it’s evident in the clip that Nat is bigger than Georgia, overpowers her and ignores her sincere frightened pleas to stop, and that she cries bitterly and curls into a foetal huddle after he lets her go. Not sure where the confusion lies or the judgement need be reserved, but go off...
The show aired long ago and I’ve not seen in a while either, so the details I give may not be exact, but here goes—when we meet the siblings they are 23 (Georgia) and 21 (Nat). Georgia has a full-time graduate job, a place of her own, and a divorce already under her belt, while Nat is a senior student with a fiancée who only returns home from Uni for holidays. Both are depicted as intelligent and mannered, from a stable, affluent, ‘Radio 4’ (sorry if that doesn’t make sense to non-Brits, it’s the best way to describe them) upper-middle class family with no history of violence whatsoever. Iirc the show creator, Phil Redmond, wrote them this way because he wanted to experiment with how an audience would take to an !ncestuous sibling couple completely opposite to the usual Deliverance stereotype—i.e. conventionally-attractive, urbane, prosperous, educated, emotionally and physically healthy, with good prospects. What is more, the siblings have a younger brother, Dan, from whom they take immense pains to shield their relationship, showing they have a conscience, a sense of shame and concern for others.
In-story, it is not explicitly or implicitly revealed which sibling began their sexual/romantic relationship or in what way, only that it started at some vague point in their highschool years—they are some 20 months apart in age, so presumably Georgia was around 17/18 and Nat 15/16 when they first crossed the line. The way the siblings describe the early days of their relationship makes it sound rather sweet and slow-burning, and it would seem that the angst and roughness crept in later on, after the two went through a grandparental bereavement, and then were briefly seperated by the lure of University life and of their family relocating. When we first meet them and get all their backstory, it quickly becomes obvious that Georgia’s failed whirlwind marriage was an attempt to drive off her own feelings for Nat as well as encourage him to seek another partner, but it hasn’t worked well, and he’s set to repeat her same mistake with his own fiancée. The abuse that creeps into their relationship later is a result of that held-over jealousy, and of their mutual exhaustion over keeping their secret for five years.
It was a very cyclical and frustrating storyline, but very compelling and unique.