I declare before you all with my whole life, whether it be long or short, shall be devoted to your service and to the service of our great imperial family to which we all belong.

An enduring figurehead devoted to her country and Commonwealth.

Queen Elizabeth II reigned for the longest of any British monarch, becoming head of state

at just 25.

Will you solemnly promise and swear to govern the people and of your possession

and the other territories to any of them belonging or pertaining,

according to their respective laws and customs?

I solemnly promise so to do.

This is the story of her life and reign told by those who knew her and worked with her.

I'm Riannon Mills, Sky's Royal Correspondent, and this is the Sky News Daily.

Born in Mayfair, London in 1926, it wasn't expected that she would one day become monarch.

Her path changed when her uncle, King Edward VIII, abdicated,

leaving her father to become King George the 6th and her as next in line to the throne.

When her father died on the 6th of February, 1952, Princess Elizabeth immediately became queen.

Oh, she was a queen, huh to be, up to be, in 1947, Elizabeth married Prince Philip, who accompanied her throughout her reign.

The bells of joy rang out in every heart. The princess and her husband made their appearance.

Of course, after 50 years of experience, I find there's a great temptation to give advice.

The trouble is that no two marriages are quite alike.

However, I think that the main lesson that we've learned is that tolerance

is the one essential ingredient of any happy marriage.

It may not be quite so important when things are going well, but it is absolutely vital when things get difficult.

And you can take it from me that the Queen has the quality of tolerance and abundance.

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