A combo image showing the wedding of Lady Diana, Princess of Wales with Prince Charles of Wales at St Paul Cathedral in London on July 29, 1981 and an image showing Kate Middleton standing at the altar with her husband to be Prince William at Westminster Abbey on April 29, 2011.

London - Two women, both married into the same rather grand family - but they could not be more different.

Lady Diana Spencer was engaged at 19, married to the Prince of Wales at 20, and was a mother before her 21st birthday.

Kate Middleton at 19 was on a gap year before going to St Andrews University, where, aged 20, she met William.

When Kate has her baby she will be well past her 31st birthday, by which time Diana’s marriage was in ruins.

And yet, the portents once looked so different.

Diana was the one with whom the world fell in love for being so young and innocent - and so smitten with her Prince.

For her part, Kate did not enjoy such public adulation at first.

She was almost in danger of overstaying her welcome in the public mind as the girlfriend of Prince William because of what was perceived as her seemingly endless determination to be his wife, and because of his doubts. And yet she is the one who now can look forward to the kind of life within the Royal Family that Diana could only dream about.

Their ages probably have something to do with it.

Diana’s friends have little doubt that had she been older - Kate’s age, say - she would have had the experience to make the marriage work, in particular, fending off the competition from Mrs Camilla Parker Bowles.

But she was young and naive. Set against Camilla, who was mature and had lived quite a lot, there could be only one victor.

For Kate, the years that she and William have been together must have toughened her because of the flak she took: “Waity Katy” and all that.

Two things helped her. One is her understanding of William’s desire to live as “normal” a life as possible - and making sure that he does.

The other is her understanding of William’s mother and how, being so young and ill-prepared, Diana simply couldn’t cope.

In everything she has learned from William, and all that shehas read, Kate knows that Diana’s greatest achievement was as a mother.

She knows that more than anything, Diana was desperate for both her sons, Harry as well as William, to be comfortable in the real world that exists beyond the palace walls.

That is the very world Kate has brought into William’s life.

Diana also spent years during what was termed the “War of the Waleses” fearing - rightly or wrongly - that Buckingham Palace courtiers were plotting to take her children away from her.

Almost 20 years on, how different life is for the contented Kate and the deliriously-happy father-to-be William. - Daily Mail