The Queen's 1937 Girl Guide uniform and fancy dress from the 1940s are among the fascinating outfits on display in an exhibition marking her 90th birthday

A new exhibition of the Queen’s public and private outfits are set to give visitors to Windsor Castle an unrivalled glimpse into her life, the Daily Mail reports.

Family wedding outfits, ceremonial robes, riding clothes and even childhood pantomime costumes - all worn by the Queen at the royal residence over the decades - are among the ensembles going on show for the first time.

Fashioning A Reign: 90 Years Of Style From The Queen's Wardrobe opens at the Berkshire castle on Saturday.

Among the items will be elaborate costumes worn by a teenage Princess Elizabeth and her sister Princess Margaret when they staged a production of Aladdin at Windsor in 1943.

Elizabeth - who played the male lead - wore a pair of cream silk pantaloons and a blue, pink and white embroidered silk top, while Margaret was ‘Princess Roxana’ in a dramatic red and gold brocade dress with Chinese-style jacket.

The sisters spent much of their time between 1941 and 1944 during the Second World War in the safety of the Royal Lodge in Windsor Castle, where they put on plays to raise money for the Royal Household Wool Fund, which supplied knitting wool for soldiers.

Also on display is Elizabeth's Girl Guide outfit - and one of her earliest childhood riding hats.

The Queen, who still enjoys riding her ponies in Windsor Great Park, is known for never wearing a hard hat, opting for a trademark headscarf instead. But as a child she was made to wear a brown peaked cap.

Caroline de Guitaut, senior curator of decorative arts at the Royal Collection, said: ‘From an off duty perspective, we have for the first time ever on display some of the Queen's own riding clothes. Riding is such a key part of the Queen's personal life.’

The 1940s-style flared-hip jodhpurs are labelled inside with ‘Princess Elizabeth November 1947’ - the month she married the Duke of Edinburgh - and are on view with a tailored navy riding jacket.

There is also a traditional hacking jacket and jodhpurs from the 1980s, three of her riding crops and some polished riding boots.

Her outfit for the blessing of the Prince of Wales and the Duchess of Cornwall's marriage, and the ensembles she wore to the weddings of the Earl and Countess of Wessex and her grandson Peter Phillips to Autumn Kelly - all in Windsor's St George's Chapel – also form part of the collection.

Her ensemble for Edward and Sophie's wedding - which included a floor-length lavender silk chiffon piece - was an unusual one royal-style wise.

Ms de Guitaut revealed: ‘It was the first time - and one of the very rare occasions - on which the Queen wore what you would generally call a fascinator.’

She added: ‘Windsor Castle is very important to the Queen. She invariably spends her weekends there. It's been said that London is the office and Windsor is the home. It's a slightly more relaxed environment.

‘She can be at home. She can drive around and ride - all the things she likes to do…..you've got the formal side, the glamorous side - the evening gowns, state dresses, ceremonial side with the garter and life when she was a child in the Girl Guides and during the war, giving pantomimes, and the family occasions.

‘It's a little bit autobiographical. It's representative of those different aspects of life at Windsor."

A host of evening gowns and Ascot hats are also on show including a white silk dress, embroidered with 2,091 shamrocks, worn by the Queen on the diplomatically delicate, historic first State Visit to the Republic of Ireland in 2011.

The exhibition is the third in a series of special displays of the monarch's fashion at royal residences in celebration of the Queen's 90th birthday.

Fashioning A Reign: 90 Years Of Style From The Queen's Wardrobe is at Windsor Castle from Saturday to January 8 2017.