In this clip from the 1947 film Heir to the Throne, Princess Elizabeth made her most famous pledge, which still rings true today: ‘I declare before you all that my whole life whether it be long or short shall be devoted to your service and the service of our great imperial family to which we all belong.’

Written by journalist for The Times and royal correspondent Dermot Morrah, the speech was delivered on her 21st birthday while she was on a three-month tour of Southern Africa with her parents, King George VI and Queen Elizabeth, and sister Princess Margaret.

While seated in the grounds of Tuynhuys in the shadow of Table Mountain in Cape Town, the young Princess used the medium of radio and film, to confidently communicate to her future subjects that the priority of her future reign would be of service to her country and the Commonwealth.

One would argue that The Queen has kept this promise tenfold. During her reign she has been patron of over 600 organisations and charities, attended thousands of official engagements and toured every country in the Commonwealth.

Summary by Michelle Davenport