Terry Johnson's Insignificance (at the Playhouse until 19 March) glitters with every kind of commendation, bestowed since its appearance in 1982. The current staging by Sheffield Theatres is the last under the artistic directorship of Michael Grandage (off to the Donmar), and is directed by Samuel West, his successor at Sheffield, with design by Tom Piper and sound by Gregory Clarke, all RSC veterans and all in top form.

Actually, for me the most amazing sight was the first thing you saw on entering -- a curtain! a big, red, shiny curtain, just like the olden days. It didn't last long -- to an opening of heavy artillery it rose on a New York hotel bedroom with neon street signs seeping through its windows. It's 1953. The world lived in the shadow of atomic power. The Cold War saw America gripped by paranoid fear of Soviet spies. And the scientists were at work on thermonuclear and neutron weapons. Johnson's play assembles four American icons whose clashes and contradictions show the flawed humans who live in and control these events.

They are 'absolute wisdom', the Professor (Einstein); 'absolute beauty', the Actress (Monroe); ignorant power, the Senator (McCarthy at the start of his Un-American activities inquiry); and thoughtless violence, the baseball player (DiMaggio, Monroe's then husband). Reality, or at least plausibility, twine with fantasy, and Johnson skilfully manoeuvres his cast in a series of two-handed dialogues.

Some are a charming surprise, like the first encounter between the lugubrious tousled Professor (Nicholas Le Prevost) and the Actress -- Mary Stockley looking ravishing in that unforgettable white dress from Seven Year Itch, and demonstrating relativity with balloons and toy trains in a scene now justly famous. Some have a sinister authenticity with the sweaty, Bourbon-swilling Senator (Gerald Horan). Most affecting, I found, was Patrick O'Kane as the Ballplayer -- horrendously violent, literally shaking with rage, childishly proud of his own fame as a chewing-gum advert, yet humbly admitting his inadequacy and pleading for a simple marriage with the children she longs for. Too late for that. In a scene unique in my theatregoing experience, the Actress, struck by the bullying Senator, has a miscarriage onstage.

How to follow? Rather clumsily. She slips out of her bloodied nightie back into the dress and has a last scientific chat with the Professor as Johnson hastily plugs in Schr-dinger's Cat and Heisenberg's Uncertainty Principle to complete his review of nuclear physics. A portentous but limp ending. Jeannine Alton