Kate Middleton's marriage to Prince William will see her become the third most beautiful royal in history, pushing Diana, the late Princess of Wales, into fourth place, according to a poll.

Miss Middleton, who will become part of the Royal family when she marries on April 29, came third in the survey, one place ahead of Diana, Princess of Wales.

Princess Grace of Monaco - also known as the Oscar-winning actress Grace Kelly - topped the list, with a 91 per cent approval rating, closely followed by Queen Rania of Jordan, on 90 per cent.

Miss Middleton had an approval rating of 84 per cent, with the late Princess Diana close behind on 82 per cent.

The survey of 127,000 people was carried out by dating website BeautifulPeople.com.

Prince Carl Philip of Sweden came top among royal men, while Princes Harry and William took the fourth and fifth spots respectively.

The brothers' father, the Prince of Wales, was voted the 10th best-looking royal male.

The Princess Royal was the lowest ranking royal in the beauty stakes, according to the poll.

Greg Hodge, managing director of BeautifulPeople.com, said: ''Kate Middleton is no typical beauty.

''But her style, deportment and immaculate grooming have clearly won her an army of admirers, propelling her to the same heights as Princess Grace and Queen Rania.

''I think the world is breathing a sigh of relief that the British monarchy can only get better looking in generations to come.''

The survey's findings are as follows:

Top 10 royal beauties: women

1. Princess Grace of Monaco

2. Queen Rania of Jordan

3. Princess in waiting, Kate Middleton

4. Diana, Princess of Wales

5. Princess Charlotte of Monaco

6. Princess Gayatri Devi

7. Princess Madeline of Sweden

8. Crown Princess Mary of Denmark

9. Princess Margaret

10. Princess Masako of Japan

(Read by Renee Haines. Renee Haines is a journalist at the China Daily Website.)