Staggeringly good, desperately sad. The boy who played Jamie inhabited the character in every word and move he made, his performance was both innate and nuanced, the umpteen "dunnos" and "I didn't do it" utterly believable. Not the primed and polished child actor we often see, but not always convincing, the Harry Potter trio, but here was an unknown, whose performance was nothing less than extraordinary.
All performances were all so good, Stephen Graham in particular, but also Ashley Walters as the DI and Erin Doherty as the psychiatrist left literally shaking by the end of what started as a good natured interview descended into a dark place upon Jamie's, explosive outbursts, red mist descending and at the heart of it, a boy with low self esteem.
The palpable anguish Stephen Graham's character exuded was so real, particularly in the very final scene, tormented by the awful act committed by his much loved child, cracking under the strain, his nerves as taut as piano wire, precipitated by an act of vandalism to his van, his livelihood, whilst all the while trying to be the strong father and husband at the helm. Truly broken as he cries his eyes out in his son's, now vacant bedroom in the closing titles. Harrowing 
I also totally understood the feelings that Ashley Walters and his female colleague felt at the end of the 2nd episode, when they exited Jamie's school after a depressing visit to interview some of his peer group, the teachers both committed and uncommitted, wrestling with gobshite kids, presenting lessons of dullness via videos.
30 years of a perfect storm of a feminised education system, I and the mothers of boys mine went to school with were well aware of that, boys continually being perceived as a nuisance, that subliminal message made some want to live that preordained role, the birth of boy children being met with a sigh from some, as if somehow the mother has missed out on the first prize, yes there have been threads over on MN on tha very subject, a lack of male teachers, I can't say I blame men not wanting to go into the profession it's a minefield, absent fathers (although not the case with Jamie) toxic male role models and of late the so called male "influencers", peddling misogyny, the objectification of girls and women, nothing new really but the availability of the most pernicious pornography so readily on tap via the smart phone, every kid has one has warped the young mind. There's so much that needs to be dealt with but the Genie is well and truly out of the bottle and has been for quite some time, how to reverse so much of what is obviously a clear and present danger to adolescents of both sexes, is only ever tinkered around the edges and talked about, I'm not sure anyone really knows how to tackle it.