Britannia rules the staves!

And so to the Dorset Garden Theatre in the London summer of 1691, where the latest semi-opera is approaching its apotheosis. "Merlin waves his Wand; the Scene changes and discloses the British Ocean in a storm. Aeolus in a cloud above; Four Winds hanging, etc." In a tremendous arioso, the God of Winds calms the billows while "An island arises . . . Britannia seated in the island with Fishermen at her feet, etc." There ensues a patriotic masque of amorous shepherds and boozy haymakers with a desce nt of Venus, forsaking her Cyprian Groves to sing, what else but "Fairest isle, all isles excelling".

Henry Purcell was still only 31 when he composed his music for King Arthur, or the British Worthy, but already famous enough to get his own way over the diction of a libretto from John Dryden, no less. Indeed, his untimely death in November 1695 at only 36 could well be seen as the major turning-point, the peripeteia of the entire history of British music - and not just because it was to take another couple of centuries for native talent of a comparable calibre to re-establish itself. For Purcell's earlier music in particular - before he began more assiduously absorbing the latest refinements of the French and Italian manners - already comes over as a synthesis of a long tradition.

How complete or conscious a synthesis might be debated - any systematic study of the musical past was still in its infancy in the 17th century. But the wonderful sequence of fantasias and In nomines he composed at the very outset of his career sounds like an explicit summing-up of an English practice already 100 years old at the time of his birth. And, fascinated as he evidently was by formal counterpoint, it is possible he could have scanned Thomas Morley's celebrated Plain and Easy Introduction to Practical Music - a textbook still circulating in Purcell's lifetime, though published in 1597 and referring, in its turn, to English masters as early as Leonel Power and John Dunstable of around 1430.

Today, thanks to an entire industry of scholarly editing, performing and recording, we can push far further back, via the sadly fragmentary 13th-century manuscript holdings of such cathedral libraries as Worcester to the very beginning of sacred polyphony before the Norman Conquest, as notated in the so-called Winchester Tropers - when it was performed, according to one admittedly disputed 10th-century account, on an "iron-toned" organ that "battered the ear" and required 70 men to pump it. All the same, the Universal Church kept a fairly close control over liturgical music throughout the Middle Ages, while the culture of the English court remained essentially French up to the time of Chaucer. Not till the end of the 100 Years War did England, let alone Britain, begin to acquire a sense of nationhood. What is striking is that it was precisely around the time of Agincourt that English music achieved more or less its sole period of international dominance: the newly euphonious counterpoint and structural reach of Power, Dunstable and such younger composers as Walter Frye vastly impressing Continental masters like Dufay and turning up in manuscripts all over Europe.

Whereupon our native talent retreated into one of its recurrent fits of introspection, elaborating the static but resplendently florid mode of polyphony to be found in the Eton Choirbook of 1490-1505, which commentators have so often likened to that other uniquely English development of the time, Perpendicular Gothic. Thereafter, the British tradition may be said to have evolved, more or less to this day, through a complex series of oscillations between insular idiosyncrasy and openness to the Continental mainstream. That oh-so-English Elizabethan madrigal fashion, for instance, of Morley and his friends was quite consciously modelled on Italian practice.

Nor was this the only historical dynamic, as the damaged state of the Eton Choirbook itself testifies. From the Reformation, during which vast quantities of old Latin church music were wantonly destroyed, to the Restoration, with its renewal of the ceremonial and theatrical activity the Puritans had suppressed, composers of the successive generations of Taverner, Tallis, Byrd, the Lawes brothers and Locke were confronted by drastic reversals of religious and political correctness.

What arguably survived through all these upheavals - apart from a penchant for certain devices and forms such as the ground bass and the fantasia - was a kind of progressive conservatism: a propensity for taking up Continental genres and reworking them in a less systematic but, as it often seems to our ears, more personal way. All this, coupled with a recurrent preference for the richly figured, the melancholic and, not least, the ambiguous, as epitomised in those major-minor clashes on the third and seventh degree of the scale to be heard in English harmony from Tallis to Purcell and, latterly, once more in Tippett.

How then to account for the apparent falling-off after Purcell? It would be unfair entirely to blame the overwhelming Italianate invasion of Handel, who, after all, half turned himself into a British composer by absorbing something of the Purcell heritage. Nor was there any dearth of native-born talent; indeed William Crotch, born in Norwich in 1775, was one of the all-time prodigies - giving his first public recital at the age of two. But somehow exceptional figures such as John Wesley's nephew Samuel,Cipriani Potter and William Sterndale Bennett all seemed to lose creative heart. It would be tempting to blame the Victorian cult of respectability - that most blighting version of political correctness. But the notion that only foreign genius ma tteredhad already inadvertently been impressed upon English audiences by the concert-giving activities of such emigres as J C Bach and Salomon in the later 18th century.

Even when that newly enterprising generation of Parry, Stanford and Elgar finally arose 100 years later, it still substantially derived from the Continental line of Mendelssohn, Schumann and Brahms. No wonder the next generation took with a vengeance to collecting what remained of the indigenous folk tradition. Yet perhaps Vaughan Williams' profoundest achievement was to reconnect with the remote past of the Tudor polyphonists - just as Tippett and Britten 30 years on were to find a new excitement in the rhetoric of Purcell himself, and Maxwell Davies still 20 years later a fresh challenge in the intricacies of Dunstable. Indeed it might be argued that, in a century in which research, performance and recording have brought the entire musical past back to present consciousness, the retrospective genius of British creativity has at last come into its own.

Anyway, the approaching Purcell tercentenary, buttressed by the centenary of the Proms, the 90th birthday, next Monday, of Sir Michael Tippett, the 60th next November of Nicholas Maw, the 50th anniversary of the premiere of Peter Grimes, and so on, seemsto be pretext enough for Radio 3's Fairest Isle festivities. No doubt our early music performers will surpass themselves; no doubt the period from Purcell to Elgar will yield some surprising rediscoveries. And no doubt the 20th-century selection will beattacked by the usual figures alleging a wicked Radio 3 disregard of their own compositions.

Perhaps, in its bounty, the network should give over a few hours for once to a kind of sonic Salon des refusees, so that we could actually decide if some of them are as good as they think themselves - though the likely upshot of the complete package willprobably be to prove that, over the last millennium, these fairest isles have produced too much in the way of genuine interest even to squeeze into the bulging schedules of an entire broadcasting year.