"Copenhagen" transferred to the Duchess Theatre in London's West End, where it ran from 8 February 1999, for more than 750 performances. It had a "second" cast when it opened in the West End, who were responsible for performing at least one of the matinee shows each week. The second cast consisted of David Baron as Niels Bohr, Corinna Marlowe as Margarethe Bohr, and William Brand as Werner Heisenberg, and after six months, they replaced the original cast for the rest of the West End run.