This is an edited version of last night's talk on Radio 4, which will be repeated on Saturday at 9.25pm on Radio 3.

In the Cabinet War Rooms, an austere, utility-furnished warren of basement offices in Whitehall, where, as the brochure says, 'everything is absolutely authentic', you can still see Winston Churchill's high, lumpy single bed. There is a battery of turquoise, scarlet and cream Bakelite telephones on view, one or two skimpy electric bar fires and lots of very ample ashtrays.

Strategic maps - of the world, of the British Empire - unfurl on the walls, with lines of coloured wool indicating the position of the armies - red for the British front line, black for the German, blue for the Free French, mauve for Vichy. Invasion is the issue, and this modest basement was the nerve centre of the resistance.

The rooms were opened to the public by the Prime Minister, Margaret Thatcher, in the spring of 1984, not long after the victory in the Falklands. They are a monument to one moment of defining national identity, opened to the public at another. There, Churchill's rousing calls, broadcast from these rooms in September 1940, are replayed to the visitor: 'These cruel, wanton, indiscriminate bombings are of course part of Hitler's invasion plan. He hopes, by killing large numbers of civilians, and women and children, that he will terrorise and cow the people of this mighty imperial city. Little does he know the spirit of the British nation. This wicked man has now resolved to break this famous island race . . .'

Churchill makes his appeal to the British as members of an island race. But the evidence of the maps on the walls around gives the lie to the image of the isolated sceptred isle, the little world all on its own. They make it clear that the nation could only survive through connection across borders, through the convoys which set out from the ports and entrepots of the Empire, her allies and sympathisers. Here they are, marked on the map: Kingston, Jamaica; Port-of-Spain, Trinidad; Aruba, Curacao, Bermuda, Puerto Rico, Recife, Halifax, St John's, Sydney, Gibraltar, Oran, Algiers, Casablanca, the Azores, Dakar, Bathurst, Freetown, Reykjavik, and many others. Other islands, a constellation of islands, other harbours, a star map of interconnection, a necklace of many stones set in as many seas, the collaboration of many peoples, places and ports; the antithesis of self-sufficiency in isolation.

The myth of national identity desires to forget this historical contingency, this interrelatedness. As a national hero, Churchill still has no rival, as Mrs Thatcher knew. In her memoirs, she remarks, with disingenuous cosiness, 'I am glad that Chequers played a large part in the Falklands story. Churchill had used it quite a lot during the Second World War and its atmosphere helped to get us all together.' Throughout, she stresses that the Falklanders are 'an island race, like the people of the United Kingdom'.

In a dreamier vein, John Major earlier also resisted encroachment from abroad, from the Continent, evoking a permanent, unchanging national idyll in his famous speech to the Conservative Europe group in the Mansion House in April 1993. The Prime Minister invoked 'a country of long shadows on county grounds, warm beer, invincible green suburbs, dog lovers - and as George Orwell said, 'old maids bicycling to Holy Communion through the morning mist'.' The Prime Minister promised, 'Britain will survive unamendable in all essentials.'

Orwell was writing in 1941, and it doesn't really need me to say that all these essentials have been through some amendments - not least that old maids might be bicycling to church to administer the sacrament as priests. The nostalgic strain of the British temper was already parodied, with cool irony, by W H Auden in The Sea and the Mirror. There, Caliban imagines a colonial servant, adrift among imperial possessions, yearning to return: 'Carry me back, Master, to the cathedral town where the canons run through the water meadows with butterfly nets and the old women keep sweetshops in the cobbled side-streets, carry me back to the days before my wife had put on weight, back to the years when the beer was cheap and the rivers really froze in winter . . . Give me my passage home . . .'

Home takes us back to a golden afternoon in the past, and this brings in the question of memory, which in turn raises history as an issue. Voltaire's epigram declares that history is une fable convenue, an agreed fable: contemporary nationalisms press agreement to their version; this is why history has become such an acute, immediate issue, why members of a democracy which wishes to survive have to take part in the telling of the story, examine and resist the self-serving fables of political ambitions.

In Zagreb, the square of the Victims of Fascism has been renamed the Square of the Croatian Kings; old tsars and old tyrants are being recovered from the annals; in Italy, Alessandra Mussolini, the granddaughter of the dictator, is even able to trade on the family name.

Arguing with the past, like paying taxes, like observing the law, like queuing, like not playing music full blast when others will be disturbed, has suddenly become a vital part of being a member of society, an ordinary but important act of citizenship, a factor in establishing the idea of home as a place you would like to belong, and might be allowed to stay. With the upheavals in Eastern Europe, Western Europe begins to stir too, and different fundamentalists have discovered the power of historical arguments to shape their reality. The British, floundering after years of authority abroad, fear loss of self when the story is changing. Rising nationalists of different stripes finger different culprits: Europe, former Commonwealth citizens, new immigrants from the former Eastern Bloc and elsewhere. And the hunger for the ascertainable, unamendable homeland turns dangerous.

While European nations struggle increasingly to define their difference from one another, another population has grown in numbers in their midst. For thousands, home has become a mythical lost continent, visible under the flux, but harder than ever to reach. The United Nations cannot even estimate how many millions of people are on the move, or will be in coming years, as new borders are being drawn on the map, year by year, sometimes week by week. Like a forest fire, they drive people into flight as they advance.

Never have there been so many newly patrolled territories, keeping one lot in and another lot out. Not since the huge emigrations at the beginning of this century have so many people looked for work in other countries. Italy, Spain and Greece, according to one report, may have a million illegal residents. In San Francisco recently, I asked a taxi driver where he was from. 'I'm an illegal,' he replied, without hesitation, as if it were a well-established nationality in itself. Homelessness, meanwhile, has become the predicament of our time.

In France, the homeless are called les sans-abri, the shelterless ones. Some of the earliest writing in the world represents a roof, an inverted 'v' on two poles, the same cipher for home that children draw in their first scribbles, alongside the stick figures of family and self. But home, in English, also encloses the idea of patria, which in French or Italian is conveyed as patrie, pays and paese, words distinct from ma maison or casa mia, and this theme lies even more acutely at the core of contemporary concerns.

Home meant native land to the earliest homeward voyager - Homer's Odysseus. For him, home was Ithaca, the land he owned and governed: home as property and place of authority.

But home ownership, that flag of Toryism, can't be translated into home in the larger sense any longer; some people may indeed have assembled their own bed from a DIY kit under their own roof in the country where they were born. But not even this assures them that they are home. Second, third, fourth generation peoples born in the US or in the UK feel themselves part of what Salman Rushdie has called, in a memorable phrase, 'imaginary homelands', countries of the mind, of memory, of history, of faith and increasingly of racial species and micro-species - nations composed of hankerings and loss, of a utopian nostalgia.

The struggle for the story of the past sets the markers on the map of the present which in turn chart the future. But memory leads down many roads: to triumphalism, on the one hand, to grudge on the other, as well as to discovery and reparation. Roots revivalism - the politics of nostalgia - can lead to reinvigorated pride among muffled or neglected peoples or groups; but remembering sufferings such as the loss of home can also be made a pretext for vengeance in the present.

Growing ethnic hatreds between peoples who share the same streets and closely resemble one another argue their cause from historical wrongs: memory and imagination pitch in to tell their stories in the contest for borders, for dominion, and for righteousness. Monsters breed in this terrible playground of fabricated identities.

At the core of the struggle for home lies the struggle for the way the story of place is told. Between what is remembered and what is forgotten, the self takes its bearings for home. The question is no longer who is to guard the guardians, but who is to tell the story? Who can bear witness?

At the heart of Romantic nationalism lies the interdependency of home, identity, heritage and women - and this mythology of the hearth continues to flourish in the present nationalist revival.

The hearthside crone who passes on the wisdom of the tribe, who epitomises the once-upon-a-time-when-all-was-well, has always been a polyglot cosmopolitan, in spite of her homely headshawl and those old regional clogs she wears and her funny beaked nose and her spinning wheel. This motley, mongrel, volatile character of folklore is of crucial importance, because even while stories are patently connected to particular places and peoples, as in the case of Hindu epics or the Irish legends, they aren't immutable. They are not even recuperable in some imagined integrity, because the act of recuperation itself and the context of the retelling affect the interpretation. The primordial past, in all its longed-for simplicity and purity, can't lie hidden inside them like a perfume still smelling in some Pharaoh's tomb. Home lies ahead, in the unfolding of the story in the future, not behind, waiting to be regained.

This romantic figment of the folk hearth returns us once more to Mum, she who embodies birthplace as well as the larger allegories of native land, and by extension of nation. But she can only fulfil this role at the price of shedding personal history, of claiming timelessness and unchangingness. Home in myth promises an end to questing, to wandering, to trouble - home is closure, the arrival brings the story to an end, with all the wicked suitors dead, the faithful dog happy in his last breath, and your wife still staunch and true at her pious task of weaving your father's shroud. Your return signals your escape from misadventures, the great public events of your career - in a sense you can now shut the door on history. The domestic hearth, coded female, burns to the side of the great events with which the returning hero busied himself.

The effect is that home does not figure at the centre of the story, nor as the product of enterprise, as the sum of the work of its members, as evolving - earned even - through men and women's labour together. In this, Odysseus, the Greek wanderer of myth, anticipates the fracture between home and factory of the industrial revolution, and the present separation between the woman's realm and the man's, women's control of household and children, men's of work and street life, with occasional homings - to Mum with the laundry, to the wife, or the girlfriend, with a bottle by way of apology. This myth disconnects home from work, makes women's tasks seem natural, timeless, somehow inevitable; it contributes to the continuing inability of our society to appreciate that raising a family and making a home is labour, as intricately bound up with economic conditions as any other kind of work.

The association of the primordial, static, authentic origin with the feminine realm runs deep in national myths, in this country, and perhaps in all of former Christendom where the Virgin Mary and her child symbolised an unsullied state of humanity and promised redemption. But England was 'Our Lady's dower', and Marian devotion flung a blue mantle of churches dedicated to her over the whole country until the Reformation. Her symbolic function then passed to queens, beginning with Gloriana or Astraea, Elizabeth I, and culminating in the present trinity of Queen Mother, Queen and Princess Diana.

An exemplary exhibition at the National Gallery in London recently interpreted the exquisite anonymous Wilton Diptych, painted around 1395. Richard II, kneeling to the Virgin, accompanied by two of England's sainted kings, Edward the Confessor and Edmund, offers an image of a new adoration of the kings, with three English monarchs in the place of the Magi, and their offering, perhaps, the country itself, whose banner, blazoned with the red cross of St George, is being held by one of the company of angels who surround the Virgin, and who wear the livery badge of the king himself, the White Hart. The banner's staff is surmounted by a tiny globe in which the tiny world, the sceptred isle, has been painted in miniature.

This icon, which gives every apparent sign of profound spirituality, in fact contains powerful partisan arguments about king and country. What is highly significant, from the point of view of modern ideas of national identity, is that when Richard II is shown extending his royal court to include heaven and the heavenly host, he is also yielding himself to a paradise of women presided over by the Virgin.

The icon's royalism, in its delicacy and sense of the sacred, would seem to have little in common with our contemporary monarchy, with Charles and Di, or Prince Philip and the Queen and the shouting headlines, the dirty tricks, the squalid eavesdropping. But they are still connected. In several respects, the Wilton Diptych conveys an enduring and vital idea of the imaginary homeland - which the Royal Family is still expected to embody. Much of the present disgust with them isn't rooted in a republican philosophy but in a nostalgic royalist idealism.

Ancient, holy and enduring - Shakespeare enshrined this idea in many plays about kingship and England, but most of all in Richard II, in John of Gaunt's ringing anthem. Here, the metaphors of heaven, island, fortress and house follow one upon the other as if by force of logic:

This royal throne of kings, this scepter'd isle,

This earth of majesty, this seat of Mars,

This other Eden, demi-paradise,

This fortress built by Nature for herself

Against infection and the hand of war,

This happy breed of men, this little world,

This precious stone set in the silver sea,

Which serves it in the office of a wall,

Or as a moat defensive to a house,

Against the envy of less happier lands,

This blessed plot, this earth, this realm, this England,

This nurse, this teeming womb of royal kings,

. . . this dear, dear land . . .

The Virgin's former dower, the enclosed and impregnable isle: aspects of the mythic kingdom present in Richard II's icon, and repeated in Shakespeare's rhetoric. Yet, at the very same time, the painting's imagery contradicts the insularity of its message. The iconography of the Wilton Dipytch, for all its ideological patriotism, draws on the Catholic church's Latin culture, jumping geographical borders, ignoring blood ties; a travelling man, as experts can tell from the techniques he used. Without these international, cultural means of expression, the diptych would be meaningless. Nativism in splendid solitude can't be achieved at all, any more than a fairy-tale can be purely home-grown.

The monarchy's symbolic role in the country's sense of identity has grown as its political power has withered. Present public anger with the Royal Family hasn't focused on constitutional flaws, or on the social damage of aristocratic privilege, but has concentrated on their behaviour - they are betraying the monarchy's mystique, the ideal of Royal Britain, defiling the chrism and the orb, the abbey and the palace, the coach and twelve, the colour trooped, all the glittering paraphernalia that the tourist boards have presented as the nation since the invention of colour photography. The personal conduct of the Royal Family, since Victoria's reign, has been expected to offer the domestic version of this sanctity, the hearthside story of national identity - with a certain class colouring, of course.

The Queen and her mother also distilled a familiar essence of Britain - with their horses and corgies, Malvern water and Earl Grey tea, cardigans, brogues, silver-framed photographs, jigsaw puzzles and the wireless, their weak and not entirely reliable menfolk. That catch-phrase, 'so very different from the home life of our own dear Queen', used to characterise anything untoward, was first spoken in Victoria's reign, and still conveys the extent to which the Queen symbolises the imaginary personality of the nation.

Could there be another way of talking about home, without harking back to nostalgic lies about the hearth, the throne, the greensward, the island race? What is home ground? And how can it be made - now, for today?

Derek Walcott was given the Nobel Prize for literature in 1992. He was born in St Lucia, when it was a British colony, and inherited through his grandparents - both black and white - a double uprootedness: on one side transportations of slaves from coastal west Africa to work sugar in the West Indies; on the other, the displacement of those colonists who, to serve the Empire, left 'home' (as England was always known, however long those colonial families of Empire had been gone).

In his poetry and drama, Walcott has worked back and forth over the relations of home and history - like the swooping swifts of the Caribbean, which he describes plying in ceaseless motion over the sea. His work puts the dominant and anguished questions of this end of the millennium: what does it mean to belong and not to belong? What way can history be told and experience be lived to bring about a sense of belonging? How does one come home?

Over the last 20 years of writing, Walcott has struggled with the Odyssean idea of home as native place, with the yearning to return to origins, and put his face against the nationalisms that assault communities and their peace, against xenophobia. As Walcott declares, 'I bear/my house inside me, everywhere'.

It is vital not to abdicate from the making of this internal dwelling place. For stories held in common make and remake the world we inhabit. Walcott reproduces the dense mesh of modern identity, with its multiple compass points, its layered experiences; he stands witness to a rich - and painful - story made in common by both invader and invaded, coloniser and colonised, migrants and residents, crossing over all moats and fortress walls, navigating the oceans, like the convoys on the map in the Cabinet War Rooms.

In a lyric poem of 1979, 'The Schooner Flight', the narrator leaves his home, breaks with his past, his roots, and ships as a seaman on board the schooner called Flight:

Though my 'Flight' never pass the incoming tide

of this inland sea beyond the loud reefs

of the final Bahamas, I am satisfied

if my hand gave voice to one people's grief.

Open the map. More islands there, man,

than peas on a tin plate, all different size,

one thousand in the Bahamas alone,

From mountains to low scrub with coral keys,

and from this bowsprit I bless every town,

the blue smell of smoke in hills behind them,

and the one small road winding down them like twine

to the roofs below; I have only one theme:

The bowsprit, the arrow, the longing, the lunging heart -

the flight to a target whose aim we'll never know,

vain search for one island that heals with its harbour

and a guiltless horizon . . .

There's no safe place from the injuries of history; home as a place or a time of innocence can only be an illusion. But the poet doesn't recover the bitter past to serve present grudges - his acts of remembering, his quest for identity are grounded in generosity.

The full text of the six lectures will be published by Vintage on 21 April at pounds 4.99.

(Photographs omitted)