LONDON - Thirty years after the fairy-tale nuptials with the unhappy ending, Britain will finally have another big royal wedding: Its dashing helicopter-pilot prince - second in line to the throne - will marry the lovely commoner who may someday become queen.

Prince William and Kate Middleton bubbled with joy Tuesday evening in their first public appearance since the palace announced their engagement after more than eight years of dating. Their wedding will be next spring or summer.

In a poignant symbol for William, his betrothed wore the sapphire and diamond engagement ring that belonged to his late mother, Diana.

"I thought it was quite nice because obviously she's not going to be around to share any of the fun and excitement of it all. This was my way of keeping her close to it all," William said.

While the romance of the two 28-year-olds is the stuff that dreams are made of, it is no exaggeration to say that the future of the Windsor dynasty depends to no small degree on the success of their union.

"We're massively excited," William said in the televised interview that marked the first time they have spoken publicly about the trials and tribulations of their love affair, which dates back to their days as university freshmen. "We're hugely excited. We're looking forward to spending the rest of our lives together."

The interview reminded many of a similar TV appearance by William's parents, Prince Charles and Diana, shortly after they became engaged.

At that time, Diana seemed frightened of the limelight and withdrew; by contrast, Middleton seemed at ease in front of the cameras. She said she wished she had met Diana, who died in a car crash in 1997.

"I would love to have met her. She's an inspirational woman," Middleton said as William looked on.

The royal wedding represents a chance for the Windsors to start anew. Middleton brings youth and glamour to a monarchy tarnished by divorce and scandal. There is already warm public support for William.

A strong, stable marriage - one that lasts decades and produces heirs - could go a long way toward undoing the damage from the ugly squabbling and televised confessions of adultery that marred the final years of Charles and Diana's tortured marriage, which began on such a high note with their spectacular wedding in 1981.

"This is their chance to rejuvenate the dynasty," said Patrick Jephson, former private secretary to Princess Diana. "This is an opportunity for a welcome national celebration."

News of the engagement was greeted with enthusiasm - and relief - in Britain. Queen Elizabeth II and her husband, Prince Philip, said they were "absolutely delighted for them both," Buckingham Palace said. Prince Charles said he was "thrilled." Middleton's parents, Carole and Michael, also gushed.

"We all think he's wonderful. We're extremely fond of him," Michael Middleton said, standing near the couple's large house in the affluent Berkshire countryside.

Royal officials said that while Middleton is commonly known as Kate, her official name is Catherine Elizabeth. She will be named Queen Catherine if William, as expected, eventually takes the throne.

Middleton, in a royal blue dress that matched the engagement ring, said she had suffered when their relationship was in trouble - including a separation that left her unhappy - but that they had grown stronger in the years they've been together.

"You go through the good times, you go through the bad times," she said, promising to "learn quickly" in her new royal role.

William proposed during a vacation in Kenya last month and gave Middleton the oval blue sapphire surrounded by diamonds from the jeweler Garrard that Charles had given his mother.

William said he carried the ring around with him for weeks as he sought the right moment to pop the question. Middleton showed the ring with obvious pride.

She described the proposal this way: "It was very romantic, and it was very personal."

The union has important implications for the monarchy's line of succession. Kate and William's first child would move ahead of his younger brother, Prince Harry, to become third in line to the throne.

Middleton acknowledged that being queen was "a daunting prospect" and declined to say whether the prince had gone down on bended knee when he proposed.

The two met as freshmen at the University of St. Andrews in Scotland, starting out as just friends but quickly becoming boyfriend and girlfriend.

"Obviously we both have a very fun time together, both have a very good sense of humor about things. We're down to earth ... and she's got plenty of habits that make me laugh that I tease her about," William said as he and Middleton faced photographers earlier Tuesday.

There is no firm date for the wedding, and the venue has not been specified. Speculation focused on St. Paul's Cathedral and Westminster Abbey.

It is not yet clear whom the elegant Middleton will choose as a dress designer, and the royal titles the couple will assume when they become man and wife have not yet been revealed.

The marriage will link Middleton - whose parents have founded a successful party supply business after working in the airline industry - with William, scion of one of the richest families in the world.

William has tried to lead a normal life, training to become a military helicopter rescue pilot, but has also become accustomed to extravagant vacations at the world's most exclusive hideaways.

As a boy, he was traumatized by his parents' very public divorce and the tragic loss of his mother. Diana died with her boyfriend, Dodi Al Fayed, in a car crash as frenzied paparazzi chased the couple through the streets of Paris, causing their inebriated driver to lose control of the vehicle.

Both William and Harry enjoy tremendous public goodwill in Britain, in part because they remind many of their mother.

While Charles and Diana often seemed tense at times during their brief courtship, William and Middleton seem relaxed and comfortable together. They are both the same age - unlike Charles and the much younger Diana - and they have lived together in shared student housing, giving them plenty of time to really know each other.

Many in Britain welcomed the royal engagement as a rare piece of good news in a time of economic uncertainty and cutbacks - a time much like 1981, when millions watched Charles and Diana's wedding.

Prime Minister David Cameron wished William and Kate "great joy in their life together," and said that when he announced the news during a Cabinet meeting, it was greeted by cheers and "a great banging of the table."

Charles' Clarence House office said he was "delighted to announce the engagement of Prince William to Miss Catherine Middleton." It used Twitter as well as a news release to alert the world.

The news had been expected for weeks as rumors about impending nuptials reached a crescendo.

"Kate has been waiting for so long, I expected her to find someone else," said London tour guide Gabrielle Sullo, 53. "The media had called her 'Waitey Katie,' so it's about time that she stopping waiting."

For pomp, the ceremony is likely to fall between the extraordinary spectacle of Charles and Diana's wedding in St. Paul's Cathedral and Charles' subdued second marriage to Camilla, duchess of Cornwall, at Windsor Guildhall in 2005.

The formal engagement is likely to turn the poised, brunette Middleton - already depicted approvingly in the fashion pages - into a global fashion icon. With her confident good looks and long brown hair, Middleton has already become one of the most photographed women in Britain.

William and Harry have spent a lifetime in the spotlight, with their drunken nights out and female friends the subject of constant tabloid gossip. William, who turned 28 in June, once told an interviewer he wouldn't marry "until I'm at least 28 or maybe 30."

William and Kate shared a house along with other students in the seaside university town of St. Andrews, where William initially studied art history before switching to geography.

In 2002, William paid 200 pounds to sit in the front row at a charity fashion show where Middleton was modeling in a daring see-through dress and black lingerie. They are thought to have started dating shortly afterward.

St. Andrews congratulated the couple, pointing out that the school has a reputation as "Britain's top matchmaking university."

Middleton is the daughter of self-made millionaires. Her father worked for an airline and her mother was a flight attendant before they started a mail-order business specializing in children's parties, run from their house in southern England.

She attended Marlborough College, an elite private school where she played tennis and field hockey, before studying art history at St. Andrews. After graduating in 2005, Middleton worked as a buyer for the fashion chain Jigsaw. She is now employed by her family's party planning business.

Palace officials said only that the wedding would be held in London. It was too early to estimate its cost.

Mark Niemierko, a luxury wedding planner based in London, said a high-end ceremony in the capital typical costs from a quarter-million pounds to a half-million pounds. ($397,000 to $794,000)

Funds will likely come out of the Civil List - money provided by Parliament to meet official royal expenses, the queen's household allowance, or drawn from her personal wealth. That is, unless Parliament votes to give the royal couple extra money for the wedding.

Taxpayers will, at the least, have to pay for security at the event, which will require large numbers of police officers.

Jenny Jones, a Green Party lawmaker at London's City Hall, said the royal family should be asked to contribute to the likely high cost of policing the wedding.

"In this age of austerity, it's unrealistic to expect the taxpayer to pay millions of pounds for policing a wedding, however beautiful. We can keep costs down by making it a low-key event or the royal family can contribute. That would seem the fairest solution," she said.

Others refused to let financial concerns mar a nearly perfect day.

"We've been waiting a long, long time for this," said Felicity Thompson, who rushed to St. James' Palace clutching a newspaper with a front-page report about the engagement. "It's a piece of history."