One of the finest movies ever made, Casablanca, celebrated its 75th anniversary last year. As I joined a nearly full house at the Duke of York’s in Brighton last Sunday, I wondered whom in the audience were watching it for the first time, and how many had seen it numerous times on television. Most chuckled in recognition of its oft-quoted dialogue, whether familiar from past viewings or references in popular culture.

“With the coming of the Second World War, many eyes in imprisoned Europe turned hopefully, or desperately, toward the freedom of the Americas. Lisbon became the great embarkation point. But, not everybody could get to Lisbon directly, and so a tortuous, roundabout refugee trail sprang up…”

The dispossessed of Europe flocked to Casablanca, their last chance to broker an Atlantic crossing. Sadly, many of them would never make that journey. There is a frantic desperation in Casablanca’s opening scenes, as several minor characters and their personal tragedies are introduced. But there is also a stink of corruption in this place where human lives are currency. The patter runs hard and fast, and gallows humour prevails.

As the cynical owner of Rick’s Café Américain, Humphrey Bogart heads a trio of heroes and villains, while a host of character actors, from Peter Lorre to Sydney Greenstreet, lend support. Rick Blaine stands uncertainly between the resistance idealism of Victor Laszlo (Paul Henreid), and the charmingly amoral French police chief, Captain Louis Renault (Claude Rains, effortlessly stealing every scene he’s in.) Born into an upper-class New York family in 1899, Bogart learned his craft on Broadway before moving to Hollywood in the 1930s. Short and rather plain-looking, his lip permanently scarred during the previous world war, Bogart got his break as runaway convict Duke Mantee in The Petrified Forest, but few could have predicted his transition to romantic lead. A consummate film icon, Bogart starred in several of my favourite movies (also including High Sierra, The Treasure of the Sierra Madre, and The African Queen.)

And what of the women? Ingrid Bergman, another legend of cinema, was already a star in her native Sweden when Hollywood came calling in 1939. In an industry built on artifice, she epitomised natural beauty. As Rick’s lost love, Ilsa Laszlo, she exudes the purity that film fans loved, but also suggests a hidden sensuality. Her story is echoed in that of Annina (Joy Page), the virtuous young Bulgarian willing to sell herself to save her husband. “Oh, but if Jan should find out,” she tells Rick. “He is such a boy. In many ways, I am so much older than he is.” Her words move Rick to pay for their transit papers, in an act of compassion that foreshadows his own sacrifice. Finally there is Yvonne (Madeleine LeBeau), the nightclub cutie who consorts with a Nazi officer after Rick callously discards her, but later redeems herself with an impassioned cry: “Vive la France!” Like many of the cast, LeBeau was an immigrant, who fled occupied France in 1940. The last surviving star of Casablanca, she passed away in 2016.

Of course, music plays a significant role in Casablanca. Singer Dooley Wilson – the only cast member who had actually visited Casablanca – plays Rick’s buddy Sam, and introduces the bittersweet love theme, ‘As Time Goes By’, along with several jauntier tunes. Perhaps the film’s most powerful sequence occurs while a group of Nazi officers are singing ‘Watch on the Rhine’, and Victor Laszlo directs cabaret singer Corinna Mura to lead the nightclub denizens in a rousing chorus of the French national anthem, creating a moment of shining humanity. In the closing frames of Casablanca, the studio orchestra reprises not ‘As Time Goes By’, but ‘La Marseillaise.’

Hurriedly released after the Allied invasion of North Africa in 1942, Casablanca was not, as some have claimed, a B-movie – the presence of Bogart and Bergman is proof of that – but the scale of its popularity and critical acclaim was unexpected. Produced by Hal B. Wallis for Warner Brothers, with its warm and witty script adapted by Julius and Phillip G. Epstein, and later Howard E. Koch from an original play, and brought to life with masterful direction by Michael Curtiz, Casablanca represents the studio system at its zenith (although novelist Jean Rhys said it did not reflect her own recollections of wartime Casablanca.) The love story of Rick and Ilsa ultimately leads them towards the greater good, with even the cunning Renault forgoing his advantage for the sake of a ‘beautiful friendship’.

Seventy-six years later, the world is facing a refugee crisis on a scale unseen since World War II. With borders closing and walls being built, it remains to be seen whether kindness will yet overcome fear. The making of Casablanca has been retold in a new book by Noah Isenberg; a biography of Michael Curtiz; and a LIFE magazine special. But for all its rich charm, Casablanca is more than a period piece: it is a warning of what may still come to pass.