With its hilariously quirky Olympic opening ceremony, a wild jumble of the celebratory and the fanciful; the conventional and the eccentric; and the frankly off-the-wall, Britain presented itself to the world Friday night as something it has often struggled to express even to itself: a nation secure in its own post-empire identity, whatever that actually is.

A maypole, still a staple of May Day celebrations in Britain, was part of the opening ceremony, conceived and directed by the filmmaker Danny Boyle. More Photos »

The noisy, busy, witty, dizzying production somehow managed to feature a flock of sheep (plus a busy sheepdog), the Sex Pistols, Lord Voldemort, the engineer Isambard Kingdom Brunel, a suggestion that the Olympic rings were forged by British foundries during the Industrial Revolution, the seminal Partridge Family reference from “Four Weddings and a Funeral,” a group of people dressed like so many members of Sgt. Pepper’s band, some rustic hovels tended by rustic peasants, “(I Can’t Get No) Satisfaction” and, in a paean to the National Health Service, a zany bunch of dancing nurses and bouncing sick children on huge hospital beds.

It was neither a nostalgic sweep through the past nor a bold vision of a brave new future. Rather, it was a sometimes slightly insane portrait of a country that has changed almost beyond measure since the last time it hosted the Games, in the grim postwar summer of 1948.

Britain was so poor then that it housed its athletes in old army barracks, made them bring their own towels and erected no buildings for the Games. The Olympics cost less than £750,000, turned a small profit and made the nation proud that it had managed to rise to the occasion in the face of such adversity.

There was that same sense of relief intermingled with self-satisfaction this time. But such was the grandeur of 2012, even in these tough economic times, that 80,000 people sat comfortably in a new Olympic Stadium, having traveled by sleek new bullet trains and special V.I.P. road lanes to a new park that has completely transformed once-derelict east London.

A little rain fell, but it hardly mattered. Queen Elizabeth II was there, after co-starring with a tuxedoed Daniel Craig, also known as James Bond, in a witty video in which she appears to parachute from a helicopter (in fact, she entered the park the usual way). Looking mystified at times — the ceremony was pitched to a generation different from hers — she presided over a bevy of lesser royals and Prime Minister David Cameron.

The first lady, Michelle Obama, was in the audience to cheer on the United States athletes, who, it must be said, did a lot of cheering for themselves anyway during the athletes’ procession. And Mitt Romney, the presumptive Republican presidential nominee, was there, too, although he was practically Public Enemy No. 1 around here after he appeared to question the British capacity for enthusiasm, something only Britons are allowed to do.

One of the biggest secrets of the night — who would light the Olympic caldron — was revealed at the end of the 3-hour-45-minute show, when seven teenage athletes took over from the British rower Steve Redgrave, who carried the torch into the stadium.  The ceremony, conceived and directed by the filmmaker Danny Boyle, was two years in the making. As is the case almost every Olympics, much of the speculation around it centered on how Britain could possibly surpass the previous summer host, China. In 2008, Beijing used its awe-inspiring opening extravaganza to proclaim in no uncertain terms that it was here, it was rich, and the world better get used to it.

But outdoing anyone else, particularly the new superpower China, was not the point for a country that can never hope to re-create the glory days of its empire. Mr. Cameron, the prime minister, said this week that London’s are “not a state-run Games — it is a people-run Games,” and Boris Johnson, the London mayor, noted sharply that Britain was not planning to “spend our defense budget” on “pyrotechnics” but would take pride in being “understated but confident.”