It is no surprise that every production of Terry Johnson's 1982 play stresses the presence of Hollywood goddess Marilyn Monroe among its characters.

More than 50 years after her death, she continues to be idolised not only as a great star of the silver screen but also as a cautionary tale of the darker downside of fame and fortune.

But, of course, Johnson's compelling and thought-provoking work also has three other cultural icons - scientific genius Albert Einstein, baseball legend Joe DiMaggio and notorious politician Joseph McCarthy - playing equally significant roles in the writer's reflections on fame, guilt and relativity.

Director Kate Wasserberg's latest production will only continue to emphasise the dominance of Monroe over the other three and it's all the fault of Sophie Melville.

Insignificance by Terry Johnson stars Sophie Melville as Marilyn Monroe at Theatr Clwyd
Insignificance by Terry Johnson stars Sophie Melville as Marilyn Monroe at Theatr Clwyd

From the moment she enters the New York hotel room occupied by Einstein in 1953, wearing THAT dress from The Seven Year Itch, Melville seduces her way into the hearts and minds of every audience member and refuses to break the spell she casts over them until the moment she exits through the same door two hours later.

This is to take nothing away from the stunning performances of Brendan Charleson as Einstein, Ben Deery as DiMaggio and Christian Patterson as McCarthy who all make the most of the grandstanding speeches each and every one of them gets to deliver.

The Ballplayer (Ben Deery) and The Actress (Sophie Melville) in Insignificance at Theatr Clwyd
The Ballplayer (Ben Deery) and The Actress (Sophie Melville) in Insignificance at Theatr Clwyd

But there is a magnetism to Melville's performance that draws your eyes and ears inexorably to her every time she is part of the action and it goes way beyond the natural mystique that forever surrounds Monroe herself.

There is no doubt the actress captures that certain something that elevated Marilyn to an immortal status denied dozens of other equally attractive and arguably more talented female stars who were competing with her during the 1950s.

Insignificance by Terry Johnson stars Sophie Melville as Marilyn Monroe and Brendan Charleson as Albert Einstein at Theatr Clwyd
Insignificance by Terry Johnson stars Sophie Melville as Marilyn Monroe and Brendan Charleson as Albert Einstein at Theatr Clwyd

Melville takes it to a whole other level, though, by portraying Monroe not as an icon on a pedestal but as a deeply flawed young woman who is loaded with brains, beauty and talent but is still capable of something as simply emotional as expressing a yearning to become a mother and live a normal life with her husband DiMaggio, a dream we know will never be fulfilled.

Of course, the impact Melville makes on the production is due in no small part to the writing of Johnson himself who provides her with probably the play's most celebrated moments when she uses a couple of flashlights and toy trains to brilliantly explain the theory of relativity to Einstein.

After witnessing this, I was convinced this speech should be made a compulsory part of every GCSE science curriculum although to guarantee it had the same impact, it would be necessary to make sure it was Sophie Melville who was delivering it!

Terry Johnson has specialised in making famous figures the central characters in his best known works, ranging from Sigmund Freud to Sidney James, although his notable conceit with Insignificance is resolutely refusing to use names, referring to his characters as The Professor, The Ballplayer, The Actress and The Senator.

Insignificance by Terry Johnson stars Sophie Melville as Marilyn Monroe and Brendan Charleson as Albert Einstein at Theatr Clwyd
Insignificance by Terry Johnson stars Sophie Melville as Marilyn Monroe and Brendan Charleson as Albert Einstein at Theatr Clwyd

Even so, some prior knowledge of the fate of these famous figures undoubtedly adds a certain poignancy to the play, not least the fact that three of them would be dead in less than 10 years and that despite the fiery nature of their soon-to-end marriage, survivor DiMaggio would remain devoted to Monroe for the rest of his life until his death in 1997.

A final word of praise for director Kate Wasserberg who adds some astonishing flourishes such as guilt-ridden Einstein's premonition of Monroe's nuclear meltdown, DiMaggio miming beating up an unconscious Monroe with an imaginary baseball bat and especially the two occasions the lights dim to reveal a breathtaking starscape on the ceiling and floor which reminds us that for all its fascinating insights, this is also a flight of fancy.

Insignificance can be seen in the Emlyn Williams Theatre at Theatr Clwyd in Mold until Saturday, October 15. Call 01352 701521 or visit www.clwyd-theatr-cymru.co.uk.