And yet this rare blend of grandness and intimacy, inside and outside, from the Corinthian pillars of the portico to the gilt decorations of the circles and the Louis IV-style backstage and foyer areas, has been achieved in a higgledy-piggledy fashion, with accretions and alterations to the original building, which dates from 1821.
Think Haymarket, you think in the modern era of John Gielgud and Oscar Wilde, of The Chalk Garden and an all-star 1962 revival of The School for Scandal (my first visit), soon followed by Alan Howard making a West End debut in The Wings of a Dove by Henry James (my second).
These thoughts raced through my mind as I welcomed to the stage nine young theatre-goers — all delightful girls, as it happens; my chorus line, perhaps — who had written reviews of The Playboy of the Western World at the Old Vic. My task was to "seminar" their writing and broaden our discussion into the issues of the play and the life and work of the vocational critic.
This, in fact, was a Haymarket Masterclass, the latest in a long-running scheme instigated by the theatre's chairman, Arnold M Crook, and administered by his delightful help mate, Hazel Kerr, and her team.
We debated the necessity or not of knowing anything about the play and its history of performance as a reviewer; the choices of emphasis and indeed subject matter even over the length of just 400 words; and the importance of writing well and double-checking your copy before pressing the send button.
Five of the girls came from Royal Holloway College, one from Moscow and the others from the Haymarket's web-site, and all had been selected in an earier process of assessment by Hazel on the basis of a "taster" review.
It was an enjoyable and rewarding experience, attended by about a hundred people sitting in the stalls. As always on these occasions, I felt I learned as much as I hope I imparted, though one nice woman in the dark asked right at the end what would have to be the catalyst to make me change my attitudes, thereby implying that I was a stick-in-the-mud with absolute views on the rights and wrongs of reviewing.
To an extent, I think she's right. Everyone's entitled to their opinion, but I think, as a serious critic, you have to earn the right to express it. And, as a reader, I don't pay any attention to a critic — in print or on line — who knows less than I do and simply can't write properly. And there's an awful lot of those around at the moment.
Arnold Crook, dapper as ever, and hot foot from attending Kim Cattrall's first night on Broadway in Private Lives, was on hand to tell me that he's got a gap in his programming schedule in February, as The Lion in Winter is not doing quite as well as he'd hoped. He wanted to know my opinion of The Last of the Duchess at the Hampstead Theatre.
And he also wanted to tell me about an extraordinary event taking place on his stage on Sunday 22 January next year, under the artistic auspices of Trevor Nunn and supported by Ray Winstone, ambassador for the Bravo 22 Company.
Bravo is an armed forces charity involving the British Legion and the Army Recovery Capability and Royal Navy Recovery Pathway: thirty wounded and sick Service personnel will write, produce and perform their own play. Their experiences have been recounted to playwright Owen Sheers who, with director Stephen Rayne, will help shape a gala performance (following a matinee) of The Two Worlds of Charlie F at 6.30pm.
Nothing could be further from the image of stuffy grandeur that in some minds clings to the dowager duchess of London theatres. But nothing could better exemplify the spirit of adventure and humanity that still runs through her gnarled old veins, and I was thrilled to experience a little bit of that life blood myself with my reviewing protegees.