We live in an age that is morally confused. Someone with more sensitivity than sense has cancelled the scheduled screenings in Piccadilly Circus today and on Sunday morning of Es Devlin and Machiko Weston’s thoughtful and moving film to commemorate the bombings of Hiroshima and Nagasaki, 75 years ago. The piece, commissioned by the Imperial War Museum, was to have been shown on the giant Piccadilly Lights screen but has now been relocated to the museum’s website, “Out of respect for the suffering caused to the people of Lebanon by the recent explosion in Beirut.” But surely it does not in any way disrespect the victims of Beirut’s terrible accident to remember those killed, maimed and poisoned in a calculated act of war in 1945.

We have a particular responsibility to remember Hiroshima and Nagasaki because Britain played a big part in bringing about this world-changing moment of destruction. Devlin and Weston have created a sombre chorus of voices, written and spoken, above and below a bright white explosive pulse across a dark screen. It starts with the English father of science fiction HG Wells imagining a supreme conquest of energy in his 1913 work The World Set Free and continues with physicist Leo Szilard’s recollection of how he conceived the atomic bomb “on a dismal grey London morning in September 1933, as I waited for a traffic light at Southampton Row.”

The very idea of using bombs from the air to destroy cities is distinctively British. When the nation stood alone in western Europe against the Nazi war machine in the early 1940s, the only way to strike Germany was from the air. This led to bombing raids that became ever more ambitious until by 1943 the RAF discovered how to use a combination of incendiaries and explosives to consume a city in an firestorm. The fire bombing of Hamburg killed over 40,000 people. That defies imagination nearly as much as the casualty figures for the two atom bombs.

So why do the bombings of Hiroshima and Nagasaki stand alone in memory when they were in fact the culmination of a strategy of causing the mass deaths of civilians? It is because history changed its nature, life on earth became forever different, in a single flash of light and heat. That’s why Devlin and Weston call their piece I Saw the World End. While western voices describe the gestation of the atomic bomb, those of its victims capture the unique experience of living through this instant. “My surroundings turned blindingly white, like a million camera flashes going off at once. Then, pitch darkness,” remembers Yasujiro Tanaka, who survived the raid on Nagasaki. Sueko Hada describes emerging from a shelter in Hiroshima to see a world utterly changed and morning become twilight.

These words are screened in a subtly paced flow like a tragic chorus. But the “western” quotes get more unsettling. There’s a lot of historical substance here. As theatre and opera designers, Devlin and Weston are used to working with complex texts and ideas: their title is a reference to Wagner’s Ring. They don’t strike an attitude. Instead they offer genuine insight from their research. Devlin tracked down the texts in English while Weston found and translated those in Japanese. They worked remotely from each other during the lockdown.

It’s not hard to understand the scientists who created the bomb. The race hate and war-lust of nazism needed stopping. Among the voices is that of Albert Einstein, writing to President Roosevelt in 1939 to state that a nuclear chain reaction might unleash “vast amounts of power” – another way of saying E=mc2.

Germany had physicists, too, even after driving many great Jewish academics such as Einstein abroad, and it had the world’s first ballistic missile, the V2 rocket. So it would have been naive not to have developed what physics declared possible. The trouble is, the atomic bomb was used on Japan, not Germany. Was that because even in the most extreme of European conflicts it was easier for the western allies to contemplate dropping it on Asians?

That is certainly what this artwork suggests. There are disturbing quotations from President Harry S Truman, who made the ultimate decision to use the new secret weapon against Hiroshima and then Nagasaki, about his hatred for “Chinese and Japs”. He’s also quoted as saying in August 1945, just after the raids, that Japan was a “beast” and had to be dealt with “as a beast”.

A defender of the decision might argue that the “beast” was the fascistic nationalism of the Japanese army, which had proved in suicidal battles for tiny islands and kamikaze attacks that it would never surrender without some awe-inspiring final defeat. Even after Nagasaki, some officers attempted to prevent Emperor Hirohito’s surrender.

But this quietly devastating work of art leaves you as uneasy and unquiet as we ought to be. The artists rightly compare the threat of nuclear war with the reality of human-caused climate change as the dire consequences of our species’ phenomenal power and hubris. Light fills the screen, spectral, godlike, unfathomable. The world ended 75 years ago and somehow we go on living.

• Watch I Saw the World End here, on the Imperial War Museum website.