The Duke of Cambridge has written the preface to Elizabeth II: The Steadfast, a biography by former Home and Foreign Secretary Lord Hurd, which recounts the reign, character and family life of The Queen.

In the preface, The Duke reflects on his grandmother The Queen's commitment to a life of public service.

The book, which will be published on 27 August 2015, forms part of series of short histories of Britain’s sovereigns entitled Penguin Monarchs, published by Penguin Books.

Preface to Elizabeth II: The Steadfast by HRH Prince William, Duke of Cambridge, 2015

Over the last ninety years, the world has changed more rapidly than at any time in history.

When my grandmother The Queen was born in 1926, the wounds of the Great War were still healing, but few would imagine how soon they would be reopened.

The confidence of the previous century had morphed into uncertainty and many worried – as they still do – about the challenge presented to our communities by rapid technological and social change.

After almost ninety years, we find ourselves in a world that has changed dramatically, almost beyond recognition to the world that The Queen was born into, but where the role of charity, family, duty and compassion perseveres.

I think I speak for my generation when I say that the example and continuity provided by The Queen is not only very rare among leaders but a great source of pride and reassurance.

Time and again, quietly and modestly, The Queen has shown us all that we can confidently embrace the future without compromising the things that are important.

From a personal point of view, I am privileged to witness the private side of The Queen, as a grandmother and great-grandmother.

The Queen’s kindness and sense of humour, her innate sense of calm and perspective, and her love of family and home are all attributes I experience first-hand.

I should add that no mention of The Queen is complete without paying tribute to my grandfather Prince Philip, who has devoted his life to supporting her.

All of us who will inherit the legacy of my grandmother’s reign and generation need to do all we can to celebrate and learn from her story. Speaking for myself, I am privileged to have The Queen as a model for a life of service to the public.

HRH Prince William, Duke of Cambridge, 2015