On the 70th anniversary of the outbreak of the Second World War, Robert McCrum considers the legacy of the greatest conflict the world has ever witnessed

When I was born in 1953, just after the coronation of Elizabeth II, I had a ration book. This flimsy, red cardboard log now looks like a passport to another country. Many things about that postwar Britain have become unrecognisable: cod liver oil, steam trains, rag-and-bone men, bobbies and telegram boys on bicycles and standing to attention for the national anthem at the end of cinema programmes.

Looking back, the black-and-white postwar images seem appropriate. Life in peacetime Britain was grey, threadbare, dreary and hopeless. There was a national sense of "Was this what we fought for?" As one American commentator put it, the British certainly believed they had won the war, but they behaved as though they had lost it.

Seventy years have gone by since the Second World War began and 64 since it ended. That dwindling minority of Britons, some 3 million, who lived through those six extraordinary years remember them as the most vivid moment in their lives and still refer to "the last war". So do the 11 million baby boomers and the 20 million over 60. Even some of their grandchildren will articulate this instinctive reflex. Britain has fought in some dozen wars and "emergencies" since 1945, but it's the Second World War that casts the longest shadow. As the D-Day anniversary celebrations indicate, this is one war that has not gone away.

Seventy years on, the experience and memory of wartime boil down to perhaps five myths that continue to condition our responses to everyday life.

First, Dunkirk. This has come to stand for the idea that in any national endeavour, especially sporting or military, Britons are almost certain to pluck defeat from the jaws of victory.

At the same time, for millions of British children, separation and loss became the defining experience of total war – evacuation, a trauma that lies at the heart of a classic like The Lion, the Witch and the Wardrobe. The evacuation to the countryside links to a third, pastoral element of Britain's wartime inheritance, expressed in the phrase "Dig for Victory". This was the idea that by the sweat of honest brows, the British could somehow survive. Shovels and spades would also be deployed in the cities, to rescue the victims of the Luftwaffe's bombardment.

The Blitz, fourth, is an essential element of Britain's wartime legacy. After the 7/7 bombings in London, the "spirit of the Blitz" was referred to ad nauseam by press and public. In contrast to the near-hysteria of many Americans after 9/11, many Britons from generations born decades after the Blitz proudly advertised the stoical repression of their feelings in a fierce display of national character .

The fifth and final inheritance of war – perhaps the ultimate peace dividend – is the sustained sense of moral superiority derived from standing alone against fascism. Roosevelt's secretary of state, Cordell Hull, wrote in his memoirs: "Never have I admired a people more than I admired the British in the summer and autumn of 1940. Even the children seemed to realise that upon their indomitable spirit depended not only their own fate, but also that of the whole democratic world."

When the war actually ended, these five strands were not yet fully encrypted into the national myth. Britain was on its knees. Wartime, and its immediate aftermath of cold and hunger, was literally a moment of deepest winter. December 1947 was the coldest of the century, another source for the frosty wastes of Narnia. Slowly, a great thaw began. By the mid-50s, green shoots were poking through. Soon there would be an age of plenty, and any amount of Turkish Delight.

The landscape would not heal so fast. I remember seeing London "bomb sites" as a child and hearing the stories of the Blitz from my grandfather, who had been a civil servant with the Ministry of Supply. A range of peculiar British institutions with first and second wartime origins continued to shape the contours of daily life: British summer time, pub closing hours, and poppy day. It was perfectly normal to see veterans in wheelchairs at bus stops or with missing limbs in railway station waiting rooms.

As children, we had a nourishing, but dreary, diet of shepherd's pie, toad in the hole, bangers and mash, fried fish and the occasional roast chicken. Institutional menus inevitably featured Spam, corned beef, lettuce and "salad cream". Powdered eggs were commonplace and so was "bread and dripping". Kia-Ora orange squash was one kind of juvenile luxury that anyone over 50 will remember, but water usually came from the tap.

Anyone who can recall these and other mundane details of everyday life, or who can remember the moment Kennedy was assassinated, is not only a citizen of postwar Britain, but is also likely to have been shaped by the age of austerity and the aftermath of total war. Broadly speaking, it amounts to the contemporary British establishment. It's quite a roll call. Let's see: the Prince of Wales (Charles Philip Arthur George Windsor), born 1948; the prime minister (Gordon Brown), born 1951; the former poet laureate (Andrew Motion), born 1952; the head of the home civil service (Sir Gus O'Donnell), born 1952; the Archbishop of Canterbury (Rowan Williams), born 1950.

Who else? Many senior figures of the British literary establishment are postwar babies: Martin Amis (1949), Julian Barnes (1946), and Ian McEwan (1948). Many vice-chancellors; several business leaders; Adair Turner of the FSA (1955); various thespians and public figures – Patrick Stewart (1940), Ian McKellen (1939), Derek Jacobi (1938); Joanna Lumley (1946), Esther Rantzen (1940), Ann Widdecombe (1947).

These names represent the 20 million for whom "the last war" continues to be an essential psychic landmark, established in everyone's mind by German Stukas screaming out of Polish skies in September 1939.

1939 will not mean much to an American, a Japanese or a Russian. For Britons of that generation, however, it's a date that sets off a cacophony of signals.

Adam Phillips, the writer and child psychotherapist, was born in 1954. How does he assess the psychic cost of war? His father, who died in 1998, fought with tanks in North Africa and apparently "loved the war". Phillips warns against glamorising the conflict, but concludes that anyone over, say, 50 is probably "more haunted than they realise by their parents' experience of war".

This haunting takes many forms, says Phillips. In the immediate aftermath of conflict, there's the extraordinary transition from states of fear and exhilaration to the routines of civilian life. Having a family and raising children in peacetime inevitably took place in "a highly disturbed emotional atmosphere". We must remember, says Phillips, that "for those who survived, the war was incredibly exciting and really unrecoverable from. There's a radical incompatibility between wartime and peacetime existence. Coming home from the war meant adjusting to the fact that the rest of your life is going to be incredibly boring".

At the same time, the wartime generation had learnt to adjust to separation, isolation and loss, and – something they would pass on to their children – to "not feeling hurt when you were hurt". To be equipped for conflict, according to Phillips, requires "self-anaesthesia", which he sees as a dominant motif in postwar British life.

Summarising the traumatic dividends of the Second World War, Phillips concludes that the postwar generations were "either envious of people who had fought in the war; or strongly identified with the dead (and no longer found life worth living); or felt they were living a kind of 'death in life'; or would ask obsessively, 'Where's the excitement?'"

As a result, Phillips contends, post-war Britons are either obsessed by loss and grief, which expresses itself in nostalgia, or obsessively pleasure-seeking, or unbearably triumphalist. When you cast your mind back over Britain's recent national landmarks, events like the Jubilee, the World Cup, royal weddings and funerals, VE Day and Armistice Day parades, you find that the dominant mood is a bittersweet mixture of pride and regret, patriotism and embarrassment, a longing to escape the curse of war mixed with the thrill of its memory, tangled up with an anxiety about the legacy of imperialism.

The shadow of "the last war" looms over the wider English-speaking world. William Cran, an award-winning documentary film-maker, was born in Australia in 1946 and came to this country as a small boy on the SS Otranto. He makes the point that not only was he growing up among adults whose conversations about the recent war were intensely vivid and influential, but also that, from the beginning of the Depression and throughout the war, more than a decade, there had been very little progress. Britain was not just in thrall to the cost of its victory, but it seemed somehow frozen in time.

Everywhere, there was bomb damage, abandoned houses and the hangovers of wartime: old newsreel footage on the BBC, ration cards and the routine disciplines of the home front. "We were incredibly thrifty," says Cran. "To this day, I can never leave food uneaten on my plate. When my mother died, I found drawers stuffed full of old envelopes she'd saved for reuse."

Cran admits that the wartime mentality lingered in other strange ways. "I used to say, 'I'm not going to go on holiday to Germany.' Italy and France, yes, but Germany, no. My big thing was not buying a German car. When I finally bought an Audi a few years ago, I had to think about it very hard." He laughs in mild self-amazement. "So you could say my war ended in 2002."

Looking back, Cran remembers the early 50s as "a happy time, but rather dull. Then there was this flashbulb moment – rock'n'roll. I remember Bill Haley and the Comets… " This was 1956; he was 10. "In my school, we used to have playground fights about the relative merits of Bill Haley and Elvis Presley versus Tommy Steele. I remember the Archbishop of Canterbury preaching a sermon against rock'n'roll. So then you knew that good things were happening."

Sometimes, history, usually so deliberate and incremental, seems to speed up in a torrent of convulsive change. The 50s were like that. Once the war was over, the aftershocks just kept on coming: Korea, Suez, the Bay of Pigs, the war in Vietnam and the death of JFK, all within 20 years of VE Day. (That, in the context of our own times, is as recent as the fall of the Berlin Wall.)

The 50s also saw perhaps the first pay-off from the war, the changing shape of women's lives. Mary Beard, a Cambridge classics professor, was born in Shropshire in 1955. For her, the significance of the Second World War was that it began the liberation of British women, paving the way for the feminist movement of the 1970s.

The Beard family's war was probably not untypical. Mary's father had "a cushy number in Cairo", but her schoolteacher mother was evacuated from the Blitz in Liverpool, first to Cheshire and then to north Wales. "For me," Beard says, "the war was all about the home front. Now, when I think about it, the experience of the war was always part of the family conversation." She says her mother found the war a liberating and politicising experience. Moving from Toxteth to a "frightfully posh" part of Cheshire, her mother came "face to face with the British class structure". All her stories of the war were of female empowerment.

"So if, as a child, I thought of the war," Beard goes on, "it was as something that was quite fun. In our family, there were no walking wounded and absolutely no losses, none. The war was a life-changing experience, certainly, but it was a positive and liberating event. My parents even had a phrase for it that I always found a bit strange. They used to say they'd had 'a good war'." She recognises now that she internalised her mother's experience.

"My mother's liberation made all the difference. She and her friends were young women in their twenties who were given unique opportunities, thanks to the war. Feminism and the feminist movement comes from these opportunities – it's Rosie the Riveter who inspired the opportunities that came to postwar women. Of course, in war women get killed, raped, etc, but it is a driver of social change. In some ways, I think that women benefited more than the working-class men from the Second World War."

Beard acknowledges the impact on her own life. "Yes, I was a low-level beneficiary," she admits. "You could say that women's careers have been assisted by the death of men."

Britain's schools have begun to change our understanding of the past, but they still reflect the experiences and values of a generation for whom "the last war" remains vivid, present, and real. Shirley Boffey is the head teacher of Coleridge primary school in Crouch End, north London. The war is real enough to her, definitely less so to the children under her care.

Shirley Boffey's father, now dead, fought at Arnhem and was always happy to reminisce about his experiences, mainly a self-deprecating account of arriving on the battlefield too late to be a hero. Her mother's war was all to do with the family's evacuation from the Channel Islands, where she had grown up.

Like Mary Beard, Boffey remembers that it was the First World War, in which her grandfather had been gassed, that made the biggest impression on her young life. "I suppose both wars fascinated me," she says, "because of my dad and my grandad."

In her own life, the legacy of war has been the ingrained habit of prudence and frugality. "War makes you cautious about the immediate future," she says. "For years, my mum kept a stock of tinned food in the cupboard. Tinned fruit, tinned soup, Spam." She laughs. "My mum still has a cupboard full of tins. I suppose it gives her a sense of security."

But when "the last war" comes up in school, it's taught in quite a theoretical way, as in: "Is war against another country a good thing?" and: "What are the justifications of war?" Or there will be an element of "living history" – cooking wartime food and making ration books. Yes, her primary school children do know who Hitler was. "We talk about the Holocaust," she says, "and we read The Diary of Anne Frank. I suppose the emphasis would be on the emotions of war, and the lesson, for the pupils, that wars come with a cost."

Schools no longer belt out "Onward, Christian Soldiers", but the Women's Institute still rallies to the singing of "Jerusalem". Britain's sense of moral superiority is not supported by churchgoing, but it persists none the less. This is the final legacy of "the last war", one that persists into the 21st century, and it seems to flow directly from the events of 1940-41, between Poland and Pearl Harbor, when the "world war" was still essentially a European conflict in which the British Isles "stood alone" against the Axis powers.

The shadow of "the last war" falls across Europe, too. I spoke to writer and documentary film-maker Nick Fraser (born 1948), who is half-French – his father, a major in D-Day invasion army, met his future wife during the Normandy campaign of 1944 – about the moral dividend Britain extracted from this period.

"Look," he says, "in Britain it always seemed simpler. We had 'a good war'. The French had 'a bad war'." Fraser is shocked to recall that he didn't really know about the Holocaust until he was about 17, but thinks this collective amnesia was deliberate.

Fraser contrasts the fall of France with Churchill's finest hour. "The defeat of the Third Republic was a horrible and humiliating experience. I never remember a single conversation about this; it was simply not spoken about. My family had a great admiration for the Brits. Anglophobia came from Paris. In Normandy, they were pleased to get rid of the Germans."

George Orwell once wrote that France in the 30s was a cross between a museum and a brothel. Fraser believes that, in the long run, France has benefited from its defeat. "Britain should get out of the habit of grandstanding on the world stage," he suggests. "We should learn to behave like the Scandinavians. The Iraq war is an example of how the memory of the Second World War makes us think in the wrong way."

Britain's apparently arrogant detachment from the European experiment comes from a mixture of geography, history and the last war. The experience of being an island that has successfully resisted invasion has become crucial to our self-image. Who can forget the Sun headline after the England football team lost an away match to Germany? "OK. You beat us at our national game, but we beat you at yours 2-0!"

British nationalism ebbs and flows in its intensity. In the early 1960s, after the years of renewal (1945-63), there was a youthful rejection of the parental message. Suddenly it was "make love, not war" and "the Summer of Love", with men and boys dressing, as Martin Amis puts it, "like clowns, not conscripts". For women, there was the lesson of their mothers' war. After the 1960s, women took charge of their lives in more and more assertive ways.

Inevitably, there would be a revolt against the backlash. The Thatcher revolution reasserted the wartime values of belligerence, stoicism, chauvinism and repression. At the same time, the closing decades of the last century saw the erosion of the social and industrial base that had sustained the war effort.

By the turn of the century, the Orwell Prize-winning historian Tony Judt writes in Reappraisals: "We have become stridently insistent – in our economic calculations, our political practices, our international strategies, even our educational priorities – that the past has nothing of interest to teach us. Ours, we insist, is a new world."

Almost, but not quite. Those for whom "the last war" has a resonance cannot escape it, even if they might want to. And in the minds of many Britons of the older generation, the fleet is still steaming up the Channel in battle grey, the RAF stands by ready to "scramble", the pound is a national symbol and the monarch is on her throne.

When adversity strikes, there is a well-rehearsed repertoire of responses on which we can fall back, with relief. As one of the Observer's interviewees (William Cran) observed, when we spoke about the impact of the credit crunch: "It feels as though I am getting back to normal. I'm saving money. I'm wearing out my shoes. If I have to, I'll dig up the garden and plant potatoes."