This was just OK. One of the weaker parts was the lack of logic in the premise and circumstances of one specific individual who went to the perilous edge of The Tower. They really didn't manage to justify her actions. It was low-motive and underwritten.
Also, an opportunity to interrogate further Why a cop with a mouth would have such a dichotomy in treatment of individuals of different race to himself was lost in this. Reinforcing the strong 'blue line' narrative, and its a baseline set of characters with protectionist morals, then putting a female gendered detective up as almost an internal affairs hound, attacking her own in the name of justice has actually been done a whole, whole lot in UK series alone. Not only is it kind of trite, but funnily enough, it practically never happens IRL.
People on here complaining about the wardrobe in a cop procedural/drama just because they recognize an actress from a more popular series? Who cares? (It was professional casual dress, except for the young female constable getting bedded by her boss. She got the butt shots in yoga tights treatment more than once when out of uniform.) Are they complaining because they can't see everyone's bits hanging out? Go watch GoT again!