Going to Southwark Playhouse is a bit like a lucky dip: you never quite know what you will get, but with the prices being what they are, the risk pays off often enough. Earlier in the year we went to see Firebird, which, were I making a ranking of plays seen in 2026, would easily make the top five.

I decided on Relative Motion because the write-up implied that it touched on coercive control and, importantly, the age recommendation was 14+. From the description, it felt exactly the right kind of play to take my daughter to, supplementing the PSHE themes she is covering at school in a more traditional way.

I was correct in my assessment. Even if it does so in a slightly too didactic manner, the play is good at exploring how something experienced as loving, exciting and safe can gradually become destructive.

As the title suggests, Relative Motion is partly about the difference between experiencing a relationship from within and observing its evolution from the outside. Sam and Paul do not initially look like an obviously unhealthy couple, either to us or to Sam. But as the relationship develops, the audience begins to recognise warning signs that she cannot yet see. Once a relationship is over, those signs can look obvious; while you are living through it, they may not.

The Isaac Newton references, while occasionally a bit heavy-handed, work reasonably well.

First law: inertia. An object remains at rest, or continues moving at a constant velocity, unless acted upon by an external force.

The play illustrates how we narrate what is happening to us, and how that narrative can cloud our judgment. Inertia, after all, applies to relationships too, or at least to the stories we tell ourselves about them. As new information emerges, we try to make it fit the story we have already constructed rather than accept it as a new external input to be reckoned with.

That feels central to Sam. It isn’t simply that she cannot see Paul’s behaviour from the outside vantage point we in the audience have. She has something invested in the story continuing as it is.

Second law: force = mass × acceleration. The acceleration of an object depends on the force acting upon it and its mass.

The second law works particularly well. Understanding the forces acting on an object allows you to understand its trajectory. This makes Sam believe she understands where her relationship is heading. The problem is that she doesn’t know all the forces acting upon it. She does not know what forces have shaped Paul into who he is today, or how they will influence the way he reacts to different events.

Third law: action and reaction. When one object exerts a force on another, the second exerts an equal and opposite force on the first.

The third law is where more nuance would be welcome. In an interview, Greenwood says that she did not want to write a story where one person was good and the other bad, describing both characters as “messy and fallible”. This, however, does not come across strongly enough.

Not because anything Sam might do would justify Paul’s behaviour. It wouldn’t. But allowing Sam to be more unreasonable could show more convincingly how someone inside a coercive relationship might come to see the other person’s reaction as justified. It is this kind of internal rationalisation that can make unacceptable behaviour easier to excuse when you are the person experiencing it. It would also make Sam’s reasons for explaining away Paul’s behaviour more psychologically credible.

But perhaps more importantly, in its determination to stick to Newton, the play does not sufficiently explore another force acting on Sam: the need to be in a relationship and to have “your person”. That basic human need for attachment and, through it, self-validation is often the reason we excuse or refuse to see what might otherwise seem quite obvious.

Nonetheless, I think this is a really good mother-and-daughter or father-and-son outing, much like John Proctor is the Villain, precisely because it is such a natural conversation starter. The intimacy of The Little auditorium adds to that feeling. You are not observing the relationship from a comfortable distance, but sitting almost alongside it as it unfolds. Not too different from your teenager relating all the school gossip and drama.

In terms of the acting, we went during previews, so my observations come with that caveat. I would say that Stephanie Greenwood, who is also the writer, is the weaker of the two as Sam. Sean Hart, playing Paul, is more compelling, particularly in the way he handles Paul’s volatility.

What needs further refinement is the closing scene. It employs the split-narrative idea that Robert Icke used so successfully in his Romeo and Juliet. But as soon as the alternative sequence of events reaches its conclusion, the play ends abruptly and the clapping begins. I was left with the odd feeling that something had suddenly been cut short, or that I had somehow missed the actual ending.

Sometimes we all need to pause, take a step back and look from the outside in. That is certainly true of relationships, and of when they end. Perhaps this ending needed to do the same.