In this first episode, with remarkable archive footage, Marr tells the childhood story of the young girl who never expected to reign. He looks closely at the influence of her grandfather, father and mother and the impact of the abdication, and hears from the Queen's grandchildren about what it must have been like to become queen at the age of 25.

In the second of three programmes, he assesses her moves to modernise the monarchy, from the abolition of the presentation of debutantes in 1958 to the very modern wedding of William and Catherine last year. Princes William and Harry are on hand to talk about their grandmother's influence on the wedding day, from the guest list to the choice of uniforms.

In the last of three programmes, Andrew Marr looks at the defining moments of HM the Queen's reign, beginning with her accession to the throne in 1952 and her Coronation sixteen months later. He examines how she has coped with decades of changing and sometimes tense relations with the media, looks backwards and forwards at royal Jubilees and charts her trip to Australia to look at what some see as her most enduring achievement, the Commonwealth. And, for the first time, all of the Queen's adult grandchildren have their say about 'The Diamond Queen'.