The man who once was among the world's most eligible bachelors has turned 30 - but things are not so bad for Prince William as he celebrates his birthday with family and friends.

Palace officials say William will mark the milestone in private with his wife, the former Kate Middleton, and perhaps some close friends. They say a low key celebration is planned.

William has been pursuing a military career as a search-and-rescue helicopter pilot while easing into married life and taking on more royal duties.

He and his wife have made a number of public appearances in recent weeks, often representing his grandmother, Queen Elizabeth II, at events to mark her Diamond Jubilee.

William also stands to inherit an estimated 10 million pounds ($1.57 million) on his birthday under the terms of the will of his late mother, Princess Diana.

The precise amount is not known because the current value of the trust set up by his mother has not been made public.

Palace officials decline to comment on William's private finances, and it is possible he may choose to leave the money in a trust.

His brother, Prince Harry, stands to inherit a similar amount when he turns 30 in 2014.

William is second in line for the throne behind his father, Prince Charles.