Always tense about premieres, he had extra reasons for sitting out on this one: not only was the new cantata, St Nicholas, his first large-scale attempt at involving professionals, amateurs and audience jointly in a musical performance, but it was also the opening event of a new style of local festival that Britten and his friends urgently hoped would prove successful enough to become annual.
It had actually been his companion, Peter Pears, who had first remarked during a prestigious but expensive European tour of their English Opera Group the previous summer: "Why not make our own festival? A modest festival with a few concerts given by friends. Why not have an Aldeburgh Festival?"
Local dignitaries were evidently impressed enough that the famous young composer of Peter Grimes had recently chosen to buy a house on their seafront; the tiny Jubilee Hall, it seemed, would do, at least for the time being. And the first Aldeburgh Festival, which ran from 5 to 13 June 1948, drew gratifyingly large audiences, including the legendary bloke in the pub during the first interval of Britten's Albert Herring who was heard to say, "I took a ticket for this show because it is local and I felt I had to. I'd have sold it to anyone for sixpence earlier on. I wouldn't part with it now for pounds 10".
With such unsolicited endorsement from the community Britten aspired to serve - and, in serving, perhaps to set a wider example to his fellow composers - it is hardly surprising that the Aldeburgh Festival became, as he put it, "the musical project I most have at heart".
Indeed, his chamber opera A Midsummer Night's Dream (1960), which opens the festival in a new production from next Wednesday, was one of no less than seven substantial musical dramas - from the one-acter The Little Sweep (1949) to his full-length testament Death in Venice (1973) - that Britten was to compose for Aldeburgh's special conditions.
Nor was his choice of standard concert repertory any less personal, what with his veneration for the "communal" Bach, his preference for the clarity of Mozart and Schubert over the thicker textures of Beethoven and Brahms, and his avoidance of the luxuriantly self-indulgent (one hardly travelled to Aldeburgh in the 1950s or 1960s to hear authoritative performances of Richard Strauss or the latest from Messiaen).
Yet aside from his own works, perhaps the most lasting influence of Britten's festival planning lay in his attitudes to the very old and the very new. In 1948, the programmes included Purcell, Dowland and Orlando Gibbons. In 1949, the Western Wynde Mass by the early Tudor composer John Taverner was heard; by 1954, Pears was singing Perotin's Beata viscera from circa 1190 AD.
And when Imogen Holst, with her family background in pioneering early music festivals, joined Britten and Pears as a third artistic director in 1956, their concern to programme composers from before Bach - many of them at that time little known or recorded - was intensified.
Schutz and Monteverdi were heard in quantity, Ockeghem and Dunstaple restored to currency and even so remote a figure as the 13th century Adam de la Halle was winkled out of the history books. It was as if the three directors simply refused to regard early music as any less contemporary than the latest offerings of their own time.
Of the established figures Britten brought to Aldeburgh, most were either personal friends - such as Tippett and Lennox Berkeley, who were heard in the first festival - or composers with whom he felt some musical affinity, such as the still-young Henze, Lutoslawski, Copland, Poulenc, Kodaly and, not least, Shostakovich who, but for illness, would have attended the 1968 Festival.
Britten was more suspicious of the serial complexities of the post-war avant-garde, though even a short piece of Stockhausen made it into an Aldeburgh programme - once. And when it came to detecting exceptional promise in the very young, Britten seemed quite unperturbed by questions of idiom. Richard Rodney Bennett was only 19 when Aldeburgh heard his 12- tone Flute Sonatina in 1955.
Nor was Britten merely acting on tip-offs in commissioning such precocious talents as the 16-year-old Oliver Knussen in l969. On the contrary, there seems to be a consensus among composers who received Britten's, always handwritten, requests for pieces, that he thought deeply about their individual gifts and the type of commission best calculated to draw them out.
So that, by the time he died in 1976, he had long since established something of an exemplary festival tradition in which - whatever the painful backstage politics and international media attention - composers and performers, professionals and amateurs, visitors and locals, could still feel what it was to share a living musical experience on a communal level.
With Britten gone and Pears in charge, over the remaining nine years of his life, surrounded by a congenial circle of performers, maybe the balance of the festival tended to tip away from the creative more towards the interpretative.
This began to be redressed with the appointment of Knussen as an artistic director in l983. And over the past decade, as executive artistic director in tandem with the conductor Steuart Bedford, Knussen has strikingly renewed Britten's commitment to new music, not only through his own elegant pieces for the festival, but by attracting an outstanding succession of composers-in- residence.
These include Lutoslawski, Takemitsu (twice), Dutilleux, Henze (twice), Schnittke, Carter, Goehr, Birtwistle, the dynamic young Finn Magnus Lindberg and, not least, that cogent and still too little-known American, Peter Lieberson, who returns again for this year's festival.
Other highlights will include a composer's portrait concert featuring that independent British spirit David Sawer, a new music-theatre piece entitled Hey Persephone! by the up-and-coming Deirdre Gribbin, and a lecture by Goehr, on the rather provocative topic of whether the whole Western tradition as encapsulated by the festival is not by now an elitist irrelevance.
But this is also the anniversary year in which Bedford and Knussen, in their turn, have chosen to bow out as directors. Next year will be planned by the still-so-young Thomas Ades - first class pianist and promising conductor as well as a composer of almost Britten-like facility and eclecticism.
The faintly decadent hedonism one seems to detect behind his post-expressionist textures sounds a world away from the satirical brilliance of early Britten.
However, Ades is also as heavily committed to other commissions and organisations as Britten ever was, and it remains to be seen whether his directorship will be extended, or whether the festival will embark upon the more risky course of appointing a different director each year.
Precedents for the latter approach, such as the South Bank's annual Meltdown festival, have not proved entirely positive. On the other hand, Aldeburgh will always retain the special continuity of the vastly varied repertoire Britten left for it - to say nothing of his fathomless bottom drawer which, as this year's concert premiere of his early radio cantata The World of the Spirit reminds one, still shows no sign of exhausting its surprises.
Aldeburgh Festival of Music and the Arts, 10-28 June; box office: 01728 453543Reuse content