Jackie Stewart, left, & Roman Polanski in Weekend of a Champion (Submarine Deluxe)

It isn’t until the present-day postscript to 1972’s Weekend of a Champion that the question is posed to Roman Polanski: What compelled you to make this film? The man asking the legendary director is a legend in his own right, Formula One driver Jackie Stewart. Polanski’s answer is a kind of shrug: I was a fan, he says, and your friend. Luckily, the documentary itself offers a more satisfying reason.

Consider me carte blanche, knowing nothing about F1 racing, and even less about Sir Jackie Stewart, “The Flying Scot.” Even so, Stewart exudes an amiable magnetism; he has the quality, perhaps derived from being so often in the public eye, of being effortlessly watchable. What’s more, he has a knack for making the complex mechanics of racing understandable and interesting to the layman.

But do not be mistaken: This behind-the-scenes portrait is in no way a guided introduction to the ins and outs of the sport. Under the direction of Frank Stewart, the film has a ’70s cool to it. There is no introduction or heavy-handed narrator. The viewer is simply dropped onto the scene, into the middle of 1971 Monaco and Stewart’s rock star reception, and left to put pieces together as he or she may.

Only as the weekend progresses do the stakes become clear. Just a week earlier, Stewart had been in a nasty crash. And recently three of his friends have died in racing accidents, a shocking piece of information first casually dropped in conversation by his wife, Helen. The understatement highlights the small moments of tension for Stewart that build as the race approaches. “A racing car is like a knife edge,” he says.

One may be drawn to the impressive footage of the driving, but even more bewitching are two sequences toward the conclusion. In the first, Stewart details how badly he “wanted” to win, and how he knew that little things would go wrong. Certainly this evocation of failure imbues the last race with additional suspense. But then Stewart pushes on and gives us a rare (for the film) moment of reflection on his sport, beginning with him wondering if fans of other drivers want to see him crash.

In the second sequence, as he climbs into his car, Stewart compares racing to being given a shot, an anesthetic, as if you suddenly lose your relation to grief and pain, but every now and then, you catch a glimpse of the “cold, hard, horrible world,” and hasten to have your shot again. It isn’t clear whether he means the world of racing or the world at large. It’s certainly hard to see 1971 Polanski and not now think about that larger world.

Whichever meaning Stewart intended, the film’s added coda provides more than its fair share of violence, showing us some truly awful crashes throughout the history of the F1. The two old friends then discuss safety advances and new regulations which have done away with a high fatality rate. The men avoid any romanticism of the high-risk, high-reward era. That task, after 90 minutes of high-octane glamour, is left to the viewer, should he or she so want it.