In those buoyant weeks before Prince William married Catherine Middleton on April 29, 2011, royal biographer Hugo Vickers was frequently asked about the world's fascination with their wedding.

"The question came up all the time. Finally the answer came to me," Vickers told before the couple's first wedding anniversary this weekend.

"The last time the man in the street really thought about Prince William was when he was a forlorn youth standing behind his mother's coffin. His marriage to Kate changed that," said Vickers on Friday from London, England.

"Suddenly the guy in the street was thinking about William again, but this time as a man who had sorted his life out and had found a nice girl to marry. This was a love match. That's what people were captivated by," he said.

Indeed, one year after their storybook wedding the Duke and Duchess of Cambridge have taken to married life in ways that have continued to fascinate the public.

Shortly after their wedding, Catherine went from walking down the aisle of London's Westminster Abbey to walking down the aisle of the couple's local supermarket.

William went straight into his duties as a search and rescue pilot.

Together, the couple made their first foreign tours of Canada and the United States and earned good reviews.

Throughout it all, these royals sent a message to the world: We're normal people, just like you. And the world took note.

"This couple is determined to do things their own way," Carolyn Harris, a royal historian at Queen's University, told

"They haven't allowed themselves to become over-exposed. That why the interest in them has continued to grow," said Harris, the editor of the website

William, 29, and Catherine, 30, also appear to have found that balance between work, their royal duties and building a private life.

"That's something Princess Diana and Prince Charles could never do," said Harris.

That happy synergy was on display during the couple's first official royal visit to Canada in 2011.

"That tour to Canada was a wonderful time. Everything they did, they did right," said Vickers.

From travelling with a scaled-down entourage to talking to people in the crowds, these newlyweds displayed an informality that set them apart from other royals.

The couple donned cowboy hats at the Calgary Stampede Parade and took part in a dragon boat race. They even took time for the prince to play street hockey with the locals in Yellowknife.

"They put a lot of spontaneity into their tour," said Harris.

"That's something we haven't seen that since the future King Edward VIII toured Canada back in 1919 and in the 1920s and he went canoeing and bought a ranch in Alberta," she Harris.

In every respect, this Canadian tour illustrated how the future King and Queen of England like to operate.

"They wanted to break down barriers and be more accessible. That endeared them to the pubic," said Harris.

Royal spell builds with pregnancy rumours

The royals plan to celebrate their first anniversary on Sunday in private, according to palace officials. But pregnancy rumours in recent weeks have brought more attention to this milestone.

"All this interest really speaks to their popularity," said Harris.

"It also says that people care about the direct royal line continuing through the Duke and Duchess of Cambridge," she said.

Royal succession can often take unexpected turns, as has been the case throughout the history of the British monarchy.

"When you look at the chart of the kings and queens of England for the past 1,000 years it's not a direct line. It's a web. Unexpected events have led to younger royal children or royal cousins succeeding to the throne," said Harris.

Forty per cent of England's monarchs have either been younger sons or children of younger sons, according to Harris. 

"There are so many prominent examples, like Henry VIII, Charles I, George V and George VI," she said.

But unlike earlier reigns in history, William and Catherine do not have to worry about a foreign monarch crossing the ocean and snatching the throne.

Without such political urgency, the Duke and Duchess can take their time to become parents. That choice illustrates a new modernity about this couple that royal watchers like.

The public has also shown enormous approval of Catherine, who has eased into her royal duties gracefully with the help of Prince William.

"The Duchess has done very well integrating into the royal family," said Harris.

"She's the first middle-class woman to marry a direct heir to the throne since Anne Hyde married the future James II in 1660. People were worried for Catherine at the beginning. But she's performed beautifully under the pressure," she said.

During her husband's absences in 2011, Catherine undertook royal engagements with the Queen and the Duchess of Cornwall and did so with ease.

"She clearly gets along with the senior members of the royal family. You can see that she is being mentored by them," said Harris.

Yet one reason, above all others, might explain the couple's enduring spell.

"Wherever they go, they don't try to upstage one another," said Vickers.

"That wasn't the case with Diana and Charles. Diana was very competitive and that irritated her husband to no end," he said.

"William and Catherine are totally in tune with one another. That makes all the difference in the world," he said.