Images of Kate Middleton already attract thousands of pounds and with media speculation rife that William is set to propose, photographers are following every move of Britain's possible future queen.

"William is very angry that nothing has changed," one courtier said of the prince's fury over the paparazzi who made life such hell for his late mother and now have increased their surveillance of his longtime girlfriend.

Ten police officers were summoned to protect the young couple after a trip to a London nightclub last week.

They keep a watchful eye as she heads off to work every day as a fashion buyer. Media reports say she has been given a police radio for her protection.

Her London apartment is constantly targeted by paparazzi, recalling the media spotlight on Diana from the moment she became the girlfriend of heir-to-the throne Prince Charles to her death in a Paris car crash in 1997 with paparazzi in hot pursuit.

William and his younger brother Harry have never forgiven the way the paparazzi hounded Diana.

Now lawyers for Middleton have written to editors urging restraint and one possible avenue is to complain to the Press Complaints Commission, the media watchdog.

Tomorrow, Middleton will celebrate her 25th birthday.

One day, she could match Diana as the world's most photographed women.

With security tightened around her, bookmakers William Hill has cut the odds of a 2007 wedding from 6-1 to 3-1.

"All the signs are pointing towards a royal engagement and wedding. It just seems to be the timing which remains to be decided," spokesman Graham Sharpe said.