It's a sign of a good play that the morning after, the complexities of the plot are still playing out in your head.

Michael Frayn’s gripping drama Copenhagen doesn't disappoint when it comes to pounding the old grey matter.

The play rails around theoretical physics - so it's not on the Finding Nemo end of the theatrical scale.

It is a muscular watch, but utterly absorbing, despite the masterclass in particle physics which warps and wefts into the plot, beautifully composed in both direction and performance from three exceptional actors.

That plot centres around one event.

In Nazi occupied Copenhagen in 1941, a clandestine encounter took place between two Nobel Prize winning physicists engaged in the development of the nuclear bomb. Werner Heisenberg, a German, and his Danish counterpart, Niels Bohr. The men were old friends and long-term colleagues, but now found themselves on opposite sides of the divide.

Malcolm Sinclair, as the avuncular Bohr, is transfixing on stage. His delivery is so well timed, and in places comedic, that he provides some light and shade in a wonderfully intense, and at times, sinister script.

Haydn Gwynne plays Bohr's wife Margerethe a slightly spikey protagonist, never doubting her husband's role, but almost conducts what at times feels like a concerto of dialogue between the three characters.

They say there is a link between mathematics and music - which seems to come out in the rhythm of performance.

Philip Arditti plays the role of Werner Heisenberg is also dazzling.

The whole experience of theatre going just out of the pandemic was a real treat, made better by friendly staff at the Theatre Royal.