Britain's Prince William and his girlfriend, Kate Middleton, were together in RAF Cranwell, England, after William received his RAF wings on April 11, 2008. ((Michael Dunlea/Associated Press))

Rumours swirled in Britain Tuesday that Prince William, heir to the British throne, and his longtime girlfriend, Kate Middleton, would soon announce their engagement and marry by 2012.

The speculation began after the U.K. newspaper News of the World reported Sunday that the couple had finally come to "an understanding that their eight-year relationship will end in marriage. It is no longer a question of if, but when."

Buckingham Palace's strategy is for the couple to be married before William's grandmother, Queen Elizabeth, celebrates her diamond jubilee in 2012, marking 60 years on the throne, the paper said.

That gives Middleton, who has been described as shy and retiring, and not used to dealing with the media, three years to learn the royal ropes, according to the newspaper.

A spokesperson for Clarence House, which is the residence of Prince Charles and his sons, William and Harry, told CBC Tuesday that the story was false, but offered no further comment.

Apparently, the pressure on William to pop the question started last Friday when he and Middleton attended the wedding of Guards officer Nick van Cutsem, who quipped to the couple: "You're next!" as he and his bride left the church.

William and Middleton, both 27, have dated off and on since meeting in 2001 at the University of St Andrew in Scotland, where they were both students.

Middleton has received an invitation from the Queen to join the royals on vacation at Balmoral this summer, so she appears to have the family stamp of approval.