When the curtain went up on Michael Frayn's challenging play Copenhagen at the Oxford Playhouse in August 1998, scientists and physicists from all over the world filled the auditorium, writes Helen Peacocke.

They were in Oxford to attend an international conference on particle physics. On finding the city also offered a new play which centred on a secret meeting in 1941 between German physicist Werner Heisenberg and his Danish counterpart Niels Bohr, whose works had opened the way into the atom, the delegates filled the theatre, and naturally invited Michael to discuss the play with them afterwards.

Copenhagen has won ten awards since it opened at the Royal National Theatre's Cotteslow Theatre in May 1998, before transferring to the Duchess Theatre for more than two years - Oxford audiences were lucky enough to see it as the Playhouse was offered a one-week run while the show was making its transfer from one London venue to another.

When it returns here this week, it will be with an entirely new cast. Anna Carteret plays Margrethe Bohr, Alexander Hanson is Werner Heisenberg, and David Horovitch takes the part of Niels Bohr. Michael Blakemore, who has collaborated on seven productions with Michael, remains the play's director.

This is not an easy play. There are no instant laughs as in other Frayn works like Noises Off. The audience has to work hard to keep up as the content goes over the heads of those with little or no understanding of physics. But don't let that put you off seeing this extraordinary and most impressive drama.