Britain’s Prince William and his fiancée Kate Middleton pose for the media at St. James’s Palace in London on Tuesday after they announced their engagement. The couple are to wed in 2011.

Kate Middleton’s engagement ring, which belonged to Diana, Princess of Wales, is seen Tuesday. Prince William said he proposed using his late mother’s ring because Diana isn’t “around to to share any of the fun and excitement of it all.”

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.”

Start of new dynasty

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At that time, Diana seemed frightened of the limelight and withdrawn; by contrast, Middleton seemed at ease in front of the cameras.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.

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.”

Proud moment

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.

A history together

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.