Lightly sketched in oil on board, the young woman eating her breakfast is still unmistakable.

A candid portrait of the Queen having breakfast, painted by the Duke of Edinburgh, is one of a previously-unseen collection of pictures going on show at Sandringham.

It shows the monarch in her younger days, wearing a bright dress, reading a newspaper at a table with bread and a jar of marmalade.

Helen Walch, the Queen's public access manager, said the undated picture was believed to have been painted in the 1950s, at Windsor Castle.

Paintings from the Royal Family's private collections have featured in previous exhibitions. This summer the museum at Sandringham, which opens on Saturday, features a display of pictures painted by royalty.

Both the Duke and Prince Charles are well-known painters. Queen Alexandra, wife of King Edward VII, was also a deft hand with a brush.

The exhibition includes a view of Egypt Alexandra painted on a visit to the country in the 1860s, signed simply 'Alix'. Next to it, there is an image of Alexandra painted by her equerry, Major Gen Sir Arthur Ellis.

A beautfiul Putto cherub peeps out of a painting by Queen Louise of Denmark (1817 - 1898). Ms Walch said painting was a popular pastime among 19th Century noble women.

'There was no TV, there was no radio, no CDs,' she said. 'so you painted, sewed or played piano.'

Perhaps most touching are the floral paintings by the Grand Duchess Olga Alexandrovna of Russia (1882 - 1960).

'After she escaped the Russian revolution and fled to Denmark, she sold paintings to support herself and her family,' said Ms Walch.

Grand Duke Michael (1821 - 1929) was forced to do the same after being stripped of his title and exiled in 1891 for marrying beneath him.

As well as paintings, the exhibition includes birthday cards drawn by younger members of the Royal Family around the turn of the last century, including a cat drawn by Princess Mary for Queen Alexandra's 59th birthday, in 1903.

There are also early photographs of Sandringham House and York Cottage, now the estate office, which was the home of King George V.