London - A landmark two-hour documentary about Queen Elizabeth II turning 90 will be screened over the Easter holidays in Britain, Buckingham Palace said on Saturday.
Featuring interviews with members of the royal family, politicians, entertainers and sports stars, Our Queen At Ninety will be broadcast on ITV television on 27 March.
The documentary will see the head of state "at work and at home", the palace said.
Queen Elizabeth turns 90 on April 21.
In her first solo interview since marrying the monarch's grandson Prince William in 2011, Kate, the Duchess of Cambridge, spoke about Queen Elizabeth's relationship with their children.
Prince George, who is third in line to the throne, was born in 2013, followed by Princess Charlotte in May last year.
Kate said the Queen was "really thrilled" to hear she had given birth to a baby girl, adding: "As soon as we came back here to Kensington she was one of our first visitors.
"George is only two-and-a-half and he calls her Gan-Gan. She always leaves a little gift or something in their room when we go and stay and that just shows her love for her family."
William also shares fond memories of his grandmother, describing how people tend to become starstruck at meeting her.
"A lot of people get very excited and sort of nervous around her. And I've seen some very comical moments. I've seen people literally faint in front of her. It's quite a startling moment as to what to do when you faint in front of the Queen.
"There's a lot of trembling knees and people can't talk sometimes. It's quite difficult talking to people when they can't talk. You don't get very far, I don't get past the hellos."
In one extract, William's father Prince Charles, Queen Elizabeth's eldest son and the heir to the throne, recalled recently saying to his mother: "'Do you realise that when you reach 90, I should have known you for 68 years!' She had to laugh a little bit."
“I said to my mother...do you realise that when you reach 90 I shall have known you for 68 years, she had to laugh"https://t.co/xFYtnESteZ— BritishMonarchy (@BritishMonarchy) March 19, 2016
Prime Minister David Cameron and Charles's younger son Prince Harry also appear in the documentary.
Official celebrations for Queen Elizabeth's birthday will take place in June with a mass street party outside Buckingham Palace and a service of thanksgiving in Saint Paul's Cathedral in London.
Queen Elizabeth is the longest-serving monarch in British history, having been on the throne since 1952.