It is really quite a simple tale - give or take a coincidence or two - and it begins on the Piazzetta in Venice.  Here the flower girls are found preparing posies for their favourite gondoliers.  And favourite among the favoured are Marco and Guiseppe Palmieri.  We see that a blindfold choice of brides and realise that by a miracle of scores of thousands of performances since 1889 the brothers have never failed to encounter Tessa and Gianetta.  Crushing down the unworthy thought that somebody always cheats on the blind side of the scrum, we move on to the arrival of the Spanish nobility.

In descending order of arrogance, they are the Duchess of Plaza Toro, daughter Casilda, the Duke of the same name, (so low as to be truly 'lower orders') Luiz, the drummer, private secretary, footman, equerry, valet, and general whipping boy.  But stop a minute -when the parental backs are turned, high born maid and lowly serfs rush to each other's arms.

Enter now the grey eminence of the play - Don Alhambra, the Grand Inquisitor.  He knows, or thinks he knows, all the state secrets: the fact, for instance, that though one of the gondolier brothers is 'lower orders', the other is 'upper crust'.  They were mixed up in infancy, but one of them was born Prince of Barataria and was put for safety against the dreaded cult of Wesleyan Methodism that was sweeping the Court) into the care of Palmieri senior.

Now if you have got that so far - two gondoliers, one of them a price but no one knows which - we can reveal the next secret.  It is that this prince was married in babyhood to Casilda, daughter of the Spanish Grandee.  Which makes Luiz, the drummer, the most hopeless non-starter in the history of fashionable matrimony.

Not to worry ... Mr. Gilbert has the matter in hand.  Pausing only to show us to what depths non-government can descend when cook and Lord Chamberlain and Secretary of State and boot-boy are declared equal and kings run errands for them all, our author comes up with his master stroke.  It seems tat after that neither Marco nor Guiseppe is truly royal: their nurse popped her own brat into the Palmieri cradle, abstracted the true prince and called him her son.  His Name?  Luiz, the drummer.  In Gilbertian drama you don't call for fingerprints or blood tests - you just kit the boy out in royal robes and get him hitched over again to the heroine before anyone can recover his breath and bawl (twenty years too late, by the way) "I forbid the banns".

Bertram Mycock - From the 1965 production