Mention Robert Carlyle and chances are your thoughts will almost immediately turn to his impressive portrayal of the sociopathic Begbie in Danny Boyle's Trainspotting. I imagine that, like me, this is where the majority of people became familiar with his name (apart from those who watched him as an island bobby in genteel police series Hamish Macbeth and, let's be frank, that show's demographic probably doesn't overlap too much with Trainspotting's audience). And very possibly they too, like me, have been waiting for the same level of performance from him since.

Not that he hasn't been in good roles since then; for example as Edinburgh hard-man John Joe McCann in the BBC's Looking After Jo Jo, or lawyer David O'Sullivan in the largely overlooked Black and White. But for every Full Monty or Angela's Ashes there's a Plunkett & Macleane, or 51st State, not to mention his two-dimensional villain in The World is Not Enough (and the less said about the derivative Eragon the better). So it is perhaps unsurprising that I came to the conclusion that I had already seen the best of Carlyle, and that said best was a raging psychopath. Fortunately, though, Summer came along and proved me wrong. While it's never going to replace Begbie as his most memorable role nor, alas, be seen by anything like as many people, his portrayal of Shaun is every bit as good.

Shaun lives with his best friend Daz (Steve Evets) and his teenage son Daniel (Michael Socha). Daz is in a wheelchair, having lost the use of his legs years ago, and has liver disease to boot. Shaun is his carer; washing him, cooking for him, taking him to the hospital and even helping out with parental responsibilities for Daniel. Facing the loss of his friend after a poor prognosis at a hospital consultation, Shaun begins to revisit his life and the events which led to his current situation. Why is it that this man should spend his life looking after a disabled man to whom he has no blood ties? And what is the reason for his obvious anger and frustration at the world?

Through flashbacks to his younger self, we begin to piece together where Shaun's life went wrong. While clearly far from stupid, Shaun struggles to write and finds expressing himself difficult. Diagnosed with an undefined 'learning disability', he faces from an early age an indifferent and ineffectual educational system, unable, or perhaps unwilling, to help. What keeps his adult self going, though, while at the same time fuelling his anger at the loss, is one sun-soaked, blissful summer, spent in the company of his best friend Daz and his girlfriend Katy. Katy is the benchmark by which all future women will be measured, and it takes no great stretch to understand that any other women there may have been in Shaun's life just don't cut it.

This idyll can't last forever, though, and as his exams approach, which he dreads due to the difficulty he has with all things academic, things begin to go wrong for Shaun. His downward spiral accelerates when Katy informs him of her parents' plans to move to another town. As Shaun unravels, the pieces are put in place for two monumental and irreversible actions which will affect the rest of his life and give answers to our questions.

Tony Slater-Ling's beautiful photography bathes the scenes with the younger Shaun in the warm hue of late afternoon summer sun, which adds to the already almost painful sense of nostalgia and longing for lost youth. Yet it also gives a warmth and a glow to the lives of the characters, and perhaps even a sense of hope, which isn't altogether gone in the scenes with the adult Shaun. The photography, along with Kenny Glenaan's low key direction, makes the most of the wit and pathos in Hugh Ellis' screenplay. There's a strong supporting cast, most notably the actor playing the adolescent Shaun, but in the end it's Carlyle's film, and it's his performance that ties it all together. Though no paragon of virtue, Shaun is a complicated, troubled yet likeable character and Carlyle's portrayal of Shaun is moving, believable and real.

While undeniably downbeat, watching Summer is a rewarding experience, and features Robert Carlyle's best performance since Trainspotting. As such, it's well worth seeking out.

I have analysed this film and found it to contain 4 out of a possible 5 nodules of filmy goodness.