The play is overstuffed with Margaret’s funny and perceptive quotes but knitting them into a dialogue that can be sustained for ninety minutes has proved hard

Older people might recall her frequent trips to Mystique cavorting with minor celebs and thugs.

And those of a certain age will remember the gorgeous teenage Margaret, her ill judged affair with a dashing RAF Officer and riding pillion on a Vespa zooming round swinging London. But beyond these ciphers, little is known of the woman who, had she been born a man, would have become King. Richard Stirling’s A Princess Undone promised to shine a light on one of the most eventful and glamorous characters of post war Britain.

It is 1993 and we are in the drawing room of her apartment in Kensington Palace (a kind of warehouse for royals). Felicity Dean is Margo and has clearly invested an immense amount of time and research in crafting her royal presence. Kittenish, coquettish, stern but always in control.

She is butlered and watered by Backstairs Billy (fiercely loyal, protective and well acted by Stirling) and they are about to destroy some potentially embarrassing letters retrieved from the ailing Queen Mother’s desk.

She opens proceedings with a Dubonet and a cigarette in a long holder, and so starts the evening of hilarious reminiscences, indiscretions, bon mot and observations about her own family – excepting, of course, her sister.

Despite the appearance of thug John Biden and chancer Tristan trying to blackmail her, there is little dramatic tension. There are some tantalising references to the pointlessness of her life, her feelings for her sister and what might have-beens, but few in the audience will have taken away any new insights.

The play is overstuffed with Margaret’s funny and perceptive quotes but knitting them into a dialogue that can be sustained for ninety minutes has proved hard.

Perhaps an Evening With format might have been better to give this astonishing woman the space to tell her story.

Rating: 3/5 stars