“The Deal,” a film written by Peter Morgan and directed by Stephen Frears (the writer and director, respectively, of “The Queen”), is a swift, incisive study into the notoriously fraught relationship between Britain’s former prime minister, Tony Blair, and its current prime minister, Gordon Brown. It begins when the two met as young MPs in 1983, and leads up to the moment when Mr. Blair took over the Labour Party in 1994. (He became prime minister in 1997.)

Directed by Mr. Frears with his customary narrative economy and verve, “The Deal,” which airs Thursday night on HBO, stretches over 90 minutes in length, though there is enough material to furnish a three-season series. Certainly, this approach to the topic has its merits — “Quick in, quick out,” as Nietzsche recommended — but it also comes at the cost of simplification, bordering on caricature. Briefly put, the moral of the film is: Brown good, Blair bad.

The first thing you notice is that Mr. Brown (David Morrissey) is a human being with verifiable blood in his veins: a gruff, Scottish workaholic who is also a warm hearted Party man still in touch with such old-fashioned virtues as loyalty, tradition, and putting the good of others before oneself. Mr. Blair (Michael Sheen, who portrayed Mr. Blair in “The Queen”), on the other hand, is also a Scot but doesn’t sound like one, and looks like a slightly reptilian replicant whose quick smile and fey, unctuous manners con everyone into thinking he’s (a) human, (b) English, and (c) Socialist, when he’s closer to being a neo-Thatcherite Tory.

The history of the pact struck between Messrs. Brown and Blair is intimately familiar to Britons but will be less so to Americans. As the film reveals, Mr. Brown was a rising star of the Labour party when, in 1983, a young lawyer named Tony Blair arrived to share a windowless office with him in the House of Commons and soon became his protégé. In different circumstances, the pair might have become rivals for the party leadership; instead, they became close friends, making their eventual falling-out all the more acrimonious. Personal chemistry — the attraction of opposites — and a shared view that the Labour Party would have to become more centrist to break the Thatcherite stranglehold on the electorate, cemented the bond.

Their understanding was that Mr. Brown would one day run for election as prime minister and that Mr. Blair would support his candidacy. By 1994, however, Mr. Blair was seen by many in the party as more appealing to the average voter. And so, at Granita, a London restaurant, the two allegedly made the titular deal in which Mr. Brown would gracefully step aside, Mr. Blair would stand for election, and then, at a vaguely defined future date, the latter would resign and allow Mr. Brown to succeed him. As we all know, Mr. Brown was made to wait 13 years, though he enjoyed unprecedented power as chancellor of the Exchequer while doing so.

Overall, the film works superbly well, particularly as an acid-tinged indictment of Mr. Blair as a man who put personal ambition first, and of “New Labour” as a hollow parody of the party’s traditional fealty to the working class. Particularly powerful is the final half hour, in which we see the differing reactions of Messrs. Blair and Brown to the unexpected death of the party’s leader, John Smith, in 1994. While Mr. Brown does the decent thing, mourning and waiting for a respectful interval to elapse before putting himself forward, Mr. Blair busily pushes all the right press buttons to undermine his friend’s position.

As a damning depiction of a successful politician, this is remarkably effective — especially since no matter how hard Messrs. Morgan and Frears work to make us dislike Mr. Blair, his rise to power never seems anything less than inevitable. In that sense, “The Deal” is both intelligent and honest. It is also clear that though the screenwriter prefers Mr. Brown, it is Mr. Blair who fascinates him. He is one of those born politicians who, in Shakespeare’s words, are “lords and owners of their faces” (“I always wanted to be an actor,” Mr. Blair admits at one point), and who, while “moving others, are themselves as stone.” Unlike Mr. Brown, who is forever buried in paperwork, Mr. Blair flits from surface to surface, a creature of mirrors and cameras and screens, a man who, in the memorable words of Mr. Blair’s famed spinmeister, Peter Mandelson (Paul Rhys), has mastered “the ugly art of keeping friends.”

The film hints that despite being a fake Scot and a fake Englishman, Mr. Blair might just be a real American. In one amusing scene, he telephones Messrs. Brown and Mandelson from his house to call for an urgent strategy meeting, then leans back on his sofa and softly strums an electric guitar as if he were in a college dorm room. Earlier, when Mr. Brown admits that he finds it difficult to talk about his personal life, Mr. Blair introduces him to the American use of the verb “share,” as in sharing one’s feelings. But does he have any? Not here he doesn’t. Nor does he have any core convictions or personality except for his belief that Labour must change. “Gordon … is just Gordon,” he says in a subtle indictment of his friend’s limitations. But Tony is … whoever you want or need him to be.

Now that Mr. Brown has been in office four months, we have a fresh perspective on “The Deal.” His first appearance at Prime Minister’s Question Time was a minor disaster: Visibly stammering and perspiring, he seemed unable to answer the questions routinely hit out of the park by Mr. Blair, to the point where his peers had to step in and help him.

Soon, however, he began to impress the populace by radiating a hypnotic aura of competence, sending the Conservatives into a panic. It was said he would soon call for a general election, ratifying himself as his own man and finally stepping out of his predecessor’s shadow. But then the opposition leader, David Cameron, made a single riveting speech, and Mr. Brown, in a poorly disguised panic, hurriedly called off his election plans.

Much of this is prefigured in the superb climactic scene of “The Deal,” in which the pact between the two men is struck over dinner. Mr. Blair admits that in many ways he is Mr. Brown’s intellectual and political inferior. Yet, if only through “a quirk of fate,” he also happens to be more likely to win a general election. Pressing his point, he adds that Mr. Brown already had a chance to run for party leadership against Mr. Smith, but (not for the first time) failed to seize the moment. With his decision not to call a general election against Mr. Cameron, history already seems to be repeating itself, and “The Deal” appears all the more prescient as a result.

bbernhard@nysun.com