‘Don’t just sit there crooning like a bilious pigeon”, says the polite and socially aware Henry Higgins (Professor of Phonetics) to flower-seller Eliza on their first encounter in Covent Garden.

Such a charmer, and what a way to launch the roller coaster relationship between the two. And how wonderfully this Oxford Operatic Society production of the classic Lerner and Loewe musical delivers the tale of class and social foibles that follows.

This is a show that has been excellently rehearsed, is enjoyably choreographed with musical panache and, above all, has been really expertly cast.

The show sweeps along with great brio, helped inevitably by that long list of instantly recalled and humable songs. At the heart of the action – and I make the assumption that no reader of this needs to know the plot of My Fair Lady – are Higgins and Eliza Doolittle.

Charlie Ross plays the professor as if the role were his own creation (that means, forget about Rex Harrison). This is an excellent piece of work, with a bit of Steed from The Avengers mixing nicely with a slice of Sherlock Holmes. Ross has a pleasant voice and uses it to good effect, but it is his strength as an actor – irascibility mixing via man-child to something along the way to lover – that is his main achievement. His performance is of West End quality.

Catharine Evans is Eliza, the biggest stage role she has hitherto taken, and she shines. Her voice is pure, from Wouldn’t It Be Loverly? onwards and especially in I Could Have Danced All Night after she has achieved the transition from Cockney to lady.

She also acts and enunciates quite hilariously at the Ascot races. On the first night, she radiated confidence, and the full house approved mightily. Jeremy Dwight plays the Watson figure of Colonel Pickering exactly as it should be played, Duncan Blagrove is a broad and enthusiastic Doolittle Senior (if obviously too young for the part) and Marilyn Moore perfectly hits the right haughty and caring notes as Higgins’s mother.

There’s a huge cast, and OOS is to be congratulated on enticing so many members and deploying them so exuberantly. Once or twice – especially at the Embassy Ball dance – the stage appeared a touch small for the sheer number of people involved; but I saw nobody bumping into anybody else. David Crewe, the director, has done a fine job of organisation, and drawn some real subtlety from his performers in a show that often felt as fresh as it must have been when it opened on Broadway.

Until Saturday. Box office: telephone 01865 305305 (www.oxfordplayhouse.com).