BRYAN CRANSTON, of “Breaking Bad” fame, has earned an Oscar nomination for his performance in “Trumbo”. But even with Mr Cranston’s debonair swagger and bristling moustache, Jay Roach’s lacklustre biopic of Dalton Trumbo, a blacklisted Hollywood screenwriter, won’t appeal to anyone except current screenwriters with masochistic tendencies. Set in the 1940s and 1950s, “Trumbo” keeps insisting that the film industry was incalculably significant at the time, and that screenwriters were some of the most significant people in it. Anyone tapping away at a screenplay on their laptop in Starbucks may be inspired by this lionising view of their profession, but they will also be depressed by how much it has changed. At the start of the film, a House Un-American Activities Committee spokesman declares that “movies are the most powerful influence ever created.” It’s a claim which would be hard to take seriously now, but in 1947 it rings so true to the likes of John Wayne (David James Elliott) and Hedda Hopper (Helen Mirren), a gossip columnist, that they put pressure on Hollywood to root out employees with Communist sympathies. One such employee is the unflappable Trumbo, a highly paid writer and so-called “swimming-pool Soviet” who hands out pro-union leaflets, but who also lives with his wife (Diane Lane) and children on a sizable ranch. He and some of his fellow radicals balk when they are asked to name their comrades at the HUAC’s hearings, assuming as they do that any “contempt of court” charges won’t stick. They assume wrongly. Dubbed “The Hollywood Ten”, Trumbo and others are fined and imprisoned. More cruelly, they are blacklisted, which means that no studio can get away with hiring them. Or so it seems. But when Trumbo leaves prison, he realises that he can sell scripts under pseudonyms and under the names of other writers. What is more, he and his buddies can sell so many of these scripts that Hollywood will be forced to admit that it can’t function without them. It is a standing joke in today's show business that writers are ranked below the catering staff on any film set. Here they are indispensable.

In a way, “Trumbo” does make a compelling case for the importance of a good screenplay, because it doesn’t have one. Adapted by John McNamara from a biography by Bruce Cook, the film is an episodic soap opera which botches some of the basic requirements of any Dalton Trumbo biopic: it doesn’t establish when he decided to write pseudonymously, or how prison affected him, or even who the Hollywood Ten are. Not that Mr McNamara is solely to blame for the film’s shortcomings. The director, Mr Roach, proved he could make lively, politically-charged docudramas with “Game Change”, a penetrating TV movie about Sarah Palin’s Vice-Presidential campaign (one imagines that he is watching Donald Trump’s progress with his notebook at hand). But “Trumbo” is too slow and portentous to deliver as the snappy, satirical con-trick caper it sometimes promises to become, and yet it is too shiny and artificial to convince as a heavyweight historical drama.

Trumbo has a climactic speech about the blacklist years being “a time of fear” and “evil” in which “scores of people lost their homes, their families...their lives”. But it is an evil which is barely glimpsed in the film. Even after being blacklisted, the hero’s main complaint is that he is in such great demand that he is too busy to celebrate his daughter’s birthday. (“You’re losing us,” laments his standard-issue loyal wife.) At his lowest ebb, he pockets $12,000 for three days’ script-doctoring, most of which he does in the bath while sipping Scotch. Not much of a martyr. Then comes the farcical moment when Kirk Douglas and Otto Preminger bump into each other on his front porch as they beg him to work on “Spartacus” and “Exodus”. “Trumbo” is less an indictment of Hollywood’s cowardice than a jobbing screenwriter’s wildest fantasy.

The sequence which will make writers really jealous concerns Trumbo’s screenplay for “The Brave One”. Never mind that it bags him an Oscar; the enviable part is that, shortly after Trumbo has had the idea for the film, he tosses the finished manuscript onto a studio boss’s desk, without giving a thought to pitches, meetings or rewrites. There are quite a few 21st-century screenwriters who would happily endure a prison sentence in exchange for a working life like that.