Our original intention had been to see Hitchcock's second version of The Man Who Knew Too Much (with Doris Day singing Que Sera, Sera, 1956), but the timing proved impossible, and instead we booked seats for Charles Frend's Scott of the Antarctic (with John Mills as Scott, 1948). This was our Christmas treat at the BFI on London's South Bank, though we knew, of course, that the second film's ending wouldn't exactly send us trilling across Waterloo Bridge to our post-screening hamburgers in Covent Garden, which is another seasonal custom.

I had seen Scott of the Antarctic before, as a small boy at a cinema in a Lancashire cotton town in the closing years of the last king's reign; or rather, at one of those theatres that alternated films with variety acts, because I think my parents took me to see a close-harmony quartet called the Radio Revellers on a different night at the same place. Until last week I had never seen it again, either at the cinema or on DVD, nor had I been tempted to watch the many scenes from it that must exist online. My memory of the film, in other words, hadn't been digitally refreshed; it was a distant memory as distant memories used to be – fragmentary, blurred, unreliable.

Before the advent of the video recorder and multichannel television, this was the natural fate of old films. They were more often imperfectly remembered than actually witnessed; and sometimes not even remembered at all as a visual experience, but as a story you had been told by a friend or a relative who could recount the plot and one or two of the more vivid scenes. London and a few other cities had cinemas and societies that were dedicated to the showing of classic films – a season of Eisenstein, say, or a weekend with Frank Capra – but elsewhere they needed to be hunted down. Lucky sightings such as these apart, your interaction with cinema history tended to be second hand. Long before I saw All Quiet on the Western Front, I knew all about the butterfly that settles just out of reach in the mud because my older brother, who had seen the film in London, took me several times through the final sequence.

The image I remembered from Scott of the Antarctic was a chocolate biscuit that some men in a tent were frying on what looked like a Primus stove (we had one of those at home). Occasional reflection in the six decades since has suggested, naturally, that it could not have been a chocolate biscuit – why would you fry one, unless in 21st-century Glasgow in a deep-fat fryer? – and that I'd been misled by its oblong shape and brown colour, which imitated a then popular biscuit called a Blue Riband. But only at the BFI last week did I begin to understand how this impression had arisen.

For a film about snow and ice, there is actually quite a lot about sweets. During the trek to the Pole, Scott's second-in-command, Edward Wilson, hands around caramels to help celebrate Christmas Day; their gilt wrappings are caught in close-up. Once at the Pole, crushed by the disappointment of having come second in the race to reach it, Scott breaks into a bar of chocolate almost as an act of consolation. In an era of rationing, when empty vending machines on station platforms could be pointed out as memorials to the cornucopian age that had existed "before the war", Wilson's caramels and Scott's chocolate had made a deeper impression on me than the shooting of the ponies or three men shivering to death in a tent. A childish reaction, but perhaps it caught something of the expedition's own longing for treats.

"I must write a word of our supper last night," Scott wrote in his diary of his last Christmas Day. "We had four courses. The first, pemmican, full whack, with slices of horsemeat flavoured with onion and curry powder and thickened with biscuit; then an arrowroot, cocoa and biscuit hoosh sweetened; then a plum pudding; then cocoa with raisins, and finally a dessert of caramels and ginger. After the feast it was difficult to move." It was pemmican that the film showed being heated on the stove, but even if I'd known of it, and how vital its protein was to the expedition's survival, my five-year-old's appetite would still have preferred a chocolate biscuit.

The killing of the ponies, which provided the curry, had provoked fewer words from Scott ("Poor beasts!"), but the film gave it the full works, so far as public taste allowed in 1948. First the pony would give a troubled neigh, then it would be led forward and past the camera, then there would be a shot that signified Captain Oates was at his unpleasant work with a pistol. This happened two or three times, and each shot would set off the dog teams barking at the prospect of fresh meat, or so the film's editing suggested. "Too much animal cruelty" was one verdict as we conducted our postmortem over our hamburgers, though the main complaint was directed not at too much realism regarding animals, but too little when it came to humans. Could Scott, Wilson, Oates, Bowers and Evans really have behaved so stoically and politely, gallant gentlemen until the very end? The two women at the table found it unbelievable that so little emotion could be shown when, for example, the expedition's last support party left the five men to carry on alone, with no hugged farewells and only a shout of "Good luck!"

I wasn't sure; perhaps it had really been like that. For example, I doubt that my grandfathers, born at roughly the same time as Bowers and Oates, ever hugged another person in public, or did very much in the way of touching at all, other than a handshake at New Year. As for stoicism, who can tell? My grandfather, who was wounded in Flanders, never talked of his time there in terms of horror and suffering, though it seems reasonable to suspect he endured some, just as Scott in his diary may have more consciously repressed any outbursts of loathing and despair among the men in the tent because he knew he was writing for posterity, which had yet to become sceptical of manliness and imperial heroics.

Scott's death was only 35 years in the past when Frend began his filming, about the same distance away as Jim Callaghan's premiership is from us now. Two global conflicts reared like mountain ranges between 1912 and 1947, but the emotional ethos that celebrated self-restraint had endured, and to that extent the event and the film were of the same time. I liked the film very much, but I remembered even as I watched it how my father had much preferred the more practical and egalitarian Amundsen, a prejudice that British socialists tended to share. The psychological histories of nations are always much more intricate than we imagine: people rarely obey en masse every media directive to feel one way or another. What Charles Frend wanted me to see was human nobility struggling against the elements. Instead, what I saw as a child were a few caramels.