Luke Whitticase’s review published on Letterboxd:
To say that this is one of the best prison dramas in recent years may seem like damning with faint praise considering the glut of bad films that are usually pushed out of the genre, but it has to be said no less that this is in some ways exceptional. The films slow start pays attention to the smaller, slower details of prison life, and while the film does eventually burst into sporadic violence, as does life on the inside so we're told. What really elevated the experience beyond its detail is some really great scene and shot direction (with a good sense of geography within scenes), a dedicated performance from Jack O'Connell, and a really unique father/son dynamic that comes into play as relationships are tested.
Some of the side characters are unfortunately throw-away but the conflict is there, and while certainly an emotionally stirring movie it never manages to fully shake the one-sided approach to its storytelling (corruption and police brutality thrown in for good measure). But besides this, its actually a surprising treat that really comes across better while watching it.