For years they've been known as Prince William and Kate Middleton, or just plain Will and Kate. But now that the wedding is over, many have been left pondering how they should refer to the royal couple.

The issue is complicated, because with the April 29 marriage came several new titles. But not all of them are expected to be used for everyday references to the couple.

According to Laura Sullivan at Clarence House (the official residence of The Prince of Wales, The Duchess of Cornwall, Prince William and Prince Harry), William and Kate should now be formally referred to as The Duke and Duchess of Cambridge.

The history of the Dukedom of Cambridge stretches back to medieval times, but it has been empty since the death of Prince George in 1904, the second person to be given the title.

The title of Duke of Cambridge is "a personal gift from the Queen, a mark of her esteem for her grandson," said Jennie Bond, an expert on the monarchy.

The new titles follow a tradition that the monarch honour members of the Royal Family at the time of their marriage. A dukedom is the highest rank in the British peerage.

Prince William is not the first Duke of Cambridge to fall in love with a commoner. Prince George refused to have an arranged marriage. He fell in love with actress Sarah Louisa Fairbrother, and they were married in 1847.

In contrast to William and Kate's relationship, which has been warmly received by the Royal Family, Prince George and Fairbrother were ostracized. Fairbrother was never given the title of Duchess of Cambridge.

Additional royal titles and ties

After his wedding, William was also given the titles of Earl of Strathearn and Baron Carrickfergus. That makes Kate the Countess of Strathearn and Baroness Carrickfergus. But according to Sullivan at Clarence House, these titles aren't expected to be used in everyday references to the couple.

The Strathearn title ties the couple to Scotland, where they met and fell in love.

The title hasn't been used since 1943, when Alastair Windsor, the second Duke of Connaught and Strathearn, died. He had taken on the title after the death of his grandfather, the third son of Queen Victoria, who had been named the Duke of Connaught and Strathearn in 1874.

Carrickfergus refers to a small town in Northern Ireland. William's barony of Carrickfergus links him to Northern Ireland and is a title that hasn't been used since 1883.

Carrickfergus means Rock of Fergus and is County Antrim's oldest town. Carrickfergus castle, which dates from about 1180, is in the town and is one of the best-preserved castles in Ireland, according to the official royal wedding website.

With files from The Canadian Press