The opening salvo of Shana Feste’s writer/director debut promises so much.

It-Brits Carey Mulligan and Aaron Johnson (cast before they were famous) are teenage lovers who go from tentatively losing their virginity with each other to a shocking, gutpunch car crash that extinguishes his life.

Following the funeral, there’s an audacious, silent take of his family travelling home in a limousine – mum Grace (Susan Sarandon), father Allen (Pierce Brosnan) and younger, second-fiddle son Ryan (Johnny Simmons) – that’s devastatingly candid and effective.

Sadly, the remainder of Feste’s misery wallow doesn’t live up to this first decisive blow. Riffing heavily from Ordinary People, her observational study of an affluent family’s heartache never approaches that Oscar winner’s sensitivity or insight.

As the Brewer family slip apart in grief – Brosnan keeping a lid on his by befriending the now-pregnant Mulligan, who moves in with them; Sarandon simmering with resentment and holding vigil beside the other vehicle’s comatose driver (Revolutionary Road’s Michael Shannon); Ryan (Johnny Simmons) huffing and puffing – Feste’s inexperience undermines her film at every turn. She copes awkwardly with extraneous plot strands (Brosnan’s mistress Jennifer Ehle) and shoehorns in scenes that lack enough focus or conviction.

Mulligan comes out best as the sweet, walkingon- eggshells Rose – she even makes bringing Brosnan to a party thrown by her hip, young friends seem like a believable character choice.

Brosnan’s climactic waterworks, however, are a bit like his singing in Mamma Mia! – something you’ll really only want to see once in your life.