A day for the people to share in a young man's journey from sadness to joy

The forecast was rain. The forecast was drizzle, and clouds and probably showers, but, actually, when a young helicopter pilot from London SW1 placed the ring on the finger of a young party-accessories supplier from Bucklebury, the sun, briefly, shone.

If this was a country deep in gloom, and worried about money, and jobs, and the future, and bothered about an awful lot of money being spent on the wedding of a very rich young man to a very thin young woman, it certainly didn't look like it. Even the people who were going to work (because some of us have to work on bank holidays) couldn't sound grudging, couldn't sound, in fact, anything other than nice.

"He seems like a nice guy," said Ben, an investment banker on the train to Liverpool Street. "I like it that everyone's excited about it," said Colin, a City trader, who said his friends had camped out. "I was at a party last night," said Katie, who works in marketing, "and everyone was saying that it's just something nice."

People on the Tube didn't seem to know that you're not meant to talk to each other. They didn't seem to know that you're meant to stare at the floor or scowl. "It's lovely to have something so positive going on," said Colleen, a nurse, who was properly dressed for a wedding in hat, suit and pearls. "I'm out to support William and Kate," said Ruth, who also works in the NHS. "I think they're lovely," said Simone, who also works in the NHS. "We could," she said, "do worse than the monarchy."

Simone, who was carrying a little blue stool, and who in her spare time teaches Scottish dancing, seemed to be speaking not just for the entire NHS, which was out in full force, but for everyone. Asked whether they were big fans of the monarchy, Rachel and Katie from Essex, who were carrying giant Union Flags, and had glitter on their cheeks, looked surprised. "Yeah, I quite like them," said Rachel. "I don't think I've ever really thought of them," said Katie. "But I think Kate Middleton's fantastic. She's really normal. She's really down to earth. I saw something," she added, "about her shopping at Warehouse. Well, so," she said, "do I!"

A young British Asian guy struggled out of Embankment Tube with a massive banner wrapped around two very long poles. "It says 'The Gurkhas are with you'," he said, looking a bit embarrassed. "I'm dropping it off for my mum." At Trafalgar Square, a trio of young British Asians were more enthusiastic. "We got interested after watching some shows on TV," said Malkesh. "It brings us all together, and it shows what we can achieve as a country. It also," he said, "shows how good we all look together".

You couldn't really say, looking at all these people, most in jeans, some in frocks and fascinators, some in sequinned Union Flag top hats, or those funny antennae things that make people look like aliens, or giant insects, that this was the most beautiful nation on earth. But you couldn't look at all these people, of different ages, and colours, and backgrounds, and sizes, and not think that there was something beautiful in that mix, and something beautiful in their getting up early, on a grey Friday in April, to get together to celebrate "something nice".

It wasn't just the fountains, and the lions, and the Union Flags that made you think that this scene, in this square, in this capital city, was as British as you get. It was, as one Canadian woman pointed out to me, the fact that so many of them, when they brushed past, as, with the crowds building up, they had to, said "Sorry".

And it was the policemen. Not nasty, kettling, baton-waving policemen, but smiling bobbies on the beat, policemen who said "Good morning!" to people as they went past, which they did a lot. "We are, after all," said one, "the Queen's servants. It is," he added, and in a tone that made you think he wasn't just thinking of bank holiday rates, "an absolute pleasure to serve in this way".

Behind him, on the cream stucco buildings that run along the edge of The Mall, people were balancing on window sills, leaning on balconies on the terrace above and leaning on balconies on the floor above the terraces. It was like a giant, multi-tiered wedding cake looming over the crowds. On his right, there was a long line of toilets. On his left, the Glastonbury and Street Musical Comedy Society were acting out, in full costume and masks, their own version of the royal wedding. They were, they said, going to round off the day by going to a burlesque cabaret.

The York family from Ashtead had camped out overnight. It was cold, they said, but "great fun". They saw Prince Andrew going to the palace. Gaby and her sister Rebecca hadn't camped, but they had gone to a party shop at Chiswick and bought crowns. "The papers tell us," said Gaby, "that the British people don't want a Royal Family any more. They go on about them having too much money, but they never go on about how much money they bring in to the country. Pomp and ceremony is what the British do extremely well. It is," she said, "well worth it".

Suddenly, behind her, a band struck up. The band was marching, in red tunics and bearskins, and beating drums. The crowd cheered and waved their flags. "We can understand," said a young banker called Jack, "the arguments against the monarchy, but when you look at the alternatives, I think it's the best option." Offering me cava, his friend Simon agreed. "I think they're genuine," he said. "It's a modern relationship. It's a tough job. They're both doing it very well."

Back in Trafalgar Square, in front of the giant screens that had been rigged up for the occasion, it was hard to disagree. When Kate Middleton, whom we must now call Catherine, or Princess William, or the Duchess of Cambridge, stepped out of her hotel and into a black Rolls-Royce, she looked, as a soon-to-be-princess probably should, beautiful. Maybe one day a handsome young prince will marry, in front of two billion people, a young woman who is plump, and a bit awkward and not conventionally attractive, but this prince didn't. He married a young woman who is pretty and graceful and poised.

When the Queen arrived at the Abbey, everyone waved their flags and cheered. When William walked up the aisle, looking shy and sweet, they said "Ah". And when Kate was helped out of the car, and her smile, and dress, was revealed to the world, they gasped. It was when William smiled at Kate, as she sat down, and she smiled back, that we remembered that was why we were here.

We were here because a decent young man, with his grandmother's sense of duty and his mother's warm heart, had fallen in love with a sweet young woman. We were here because he had tested that love over 10 years, and decided that he wanted to make that love that had already been tested into something that would last for life. We were here not because we believed, as we wanted to 30 years ago, in fairy tales, but because we wanted to believe in happiness.

When "Guide me, O thou great Redeemer" echoed through Trafalgar Square, it didn't sound like the soundtrack to another age. It sounded like a reminder that princes, as well as people in public squares who watch them, also sometimes want someone to make their "anxious fears subside". When the anthem, specially commissioned from John Rutter, and sung by choir boys with voices that really did sound like angels, rang out, it sounded like something that might, if just for this hour, make everybody's anxious fears subside. And when the prayer, written by William and Kate, was read by the Bishop of London, asking for help to "be generous with our time and love and energy", it sounded like a prayer from the heart.

The couple were married, and the sun came out. The congregation sang "Jerusalem" and quite a lot of people in Trafalgar Square did, too. Confetti fluttered above us in the sky and then, surreally, above us on the screens. Champagne corks popped. Some tears were wiped away.

On this spring day in April, when the sun came out, people cried and cheered and sang not because they care passionately about the monarchy, but because, at a time when some people are losing their jobs, and worrying about money, and other people are losing their homes, or their lives, through earthquakes or storms, and other people are being gunned down by their governments for wanting the right to vote, this was "something nice". And because a very nice young man who learnt about death when he was far too young, and who had to walk behind a coffin in front of the eyes of the world, had swapped his sadness for joy. And because we, knowing this, wanted to show him ours.

The Kiss, by Tracey Emin

"It was the moment everyone was waiting for, because you want to know that it's real.

"After that kiss, you realise it isn't just splendour and pomp: it is two people in love. I'm talking about the second kiss, of course. The first one was so quick I almost missed it. The second kiss definitely looked like a snog; a proper kiss.

"They looked really naive and natural, like a child's fantasy of a bride and groom. This was an incredible day of pageantry and, above all, Britishness."