LONDON - As Prince William’s wife Catherine prepares to give birth to a new heir to the throne, she faces renewed comparisons with her late mother-in-law, Princess Diana, whom she never met.

The former Kate Middleton only met her prince four years after Diana’s untimely death, but William gave her his mother’s sapphire ring on their engagement, saying “it was right to put the two together”.

Despite the popularity of the young royals, Catherine, 31, has at times been compared unfavourably to the late princess, who seduced the public with her outspokenness and glamour.

One columnist even called her “Diana lite”. Diana’s human touch made her a potent symbol; she was described as the “people’s princess” and said she wanted to be “queen of people’s hearts”.

Like her, Catherine, whose title is Duchess of Cambridge, pays informal visits to sick children and backs addiction charities; like Diana, she is a fashion trendsetter whose choices of dress often prompt a rush on stores. But the duchess has so far opted for a far quieter public persona. When she issued a charity broadcast in April, celebrity magazine OK! - exaggerating just a little - urged readers to “hear Kate Middleton speak for the first time!”