The exhibition is being held at Windsor Castle

Works in the Windsor Castle exhibition include the first picture taken of her aged just five weeks, and her official 80th birthday portrait by Lord Snowdon.

Also featured is a new portrait by fellow octogenarian Jane Bown.

The black-and-white picture portrays the Queen, who turns 80 on 21 April, as a benevolent grandmother in pearls.

Mrs Bown, who has worked for the Observer newspaper since the 1940s, is famed for taking natural, black-and-white photographs of stars including Bertrand Russell, Cilla Black and Mick Jagger.

Tracing the Queen's public and private life over the past 80 years In pictures

Other notable subjects she has portrayed over the decades include figures such as Samuel Beckett, Noel Coward, Elizabeth Taylor and. most recently, Conservative leader David Cameron.

Royal Photographic Collection curator Sophie Gordon said of the portrait, being shown publicly for the first time: "It seems to occupy a middle ground between formal and informal.

"You get the feeling that this is a real moment in time that has been captured - there seems to be something going on, perhaps a thought passing through her mind."

The photographs in the exhibition have been selected to give a balance of formal and informal shots, as well as showing the Queen in a variety of different settings.

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They include shots of the Queen with her family, with pets, at her father's accession to the throne, at state visits and of her 1947 wedding to Lieutenant Philip Mountbatten.

"It's quite surprising, particularly for the younger generation, to see these photographs of quite a young woman looking so glamorous and fashionable and quite beautiful, like a film star," she said.

"That's not an image of the Queen we are used to."

The Queen's 80th birthday falls on 21 April and she will celebrate her official birthday on 17 June.

The exhibition is open from Monday.