JAMES PHILLIPS’S play is the story of Ethel and Julius Rosenberg, who perished on the electric chair for allegedly passing atomic warfare secrets to the Soviet Union.

While the names have been changed and there is some dramatic licence, essentially it’s the authentic history.

The central focus is the American-Jewish couple Esther and Jakob Rubenstein, devoted soulmates with a passion for communism, while Esther’s brother David and his soon-to-be-wife Rachel also shape the drama.

Perspective is provided when the play intermittently moves forward to the 1970s, where the Rubensteins’ son, Matthew, and David and Rachel’s daughter, Anna, accidentally meet and are forced to grapple with their shared legacy.

Premiered in 2005, it’s an award-winning play with significant relevance today. It paints a picture of a US maddened by paranoia, protectionism and xenophobia — a world where political allegiance divides families and communities.

And it explores the power of “the big idea,” in this case communism. Jakob, the passionate believer, gives a nerve-tingling account when he speaks of the responsibility he bears for his parents who, in the poverty of the Depression, were deprived of their dignity while others basked in privilege. “Someone’s got to stand up,” is his heartfelt cry.

And, as his execution approaches, and all but his wife seem to abandon him, he asserts of the Russian Revolution: “That revolution was an idea. There is no bigger idea than that.” With those words he challenges the prevailing assumptions of the capitalist world from that day to this.

“We will be murdered by the government of the United States,” he says in the voice of a man resigned to his fate.  

Whether the charges were true against the couple is still in question. Certainly, Ethel Rubinstein seemed to have been wrongly charged and the Soviet Union was at the time an ally of the US, not a declared enemy and the alleged secrets were widely considered to be trivial as it already had the information.

Her brother David, also implicated, did a deal with the government and retreated from the cause to be a family man. At the time, it split opinion and still does today.

The ideas that emerge from the play are crucially relevant and they highlight a genuine cause celebre that gets the blood pumping. Structurally, though, the play is uneven and somehow misses the kind of dramatic confrontations an Arthur Miller might have provided.

The cast do their best and there is a surprising authenticity from this British writer in conveying US realities. But, ultimately, it’s a cerebral piece which could do more to capture the emotions and which, with so many ideas, fails in the end to construct a central thesis.

Runs until April 13, box office: southwarkplayhouse.co.uk.