By Martha Cliff PUBLISHED: 08:58 EST, 14 February 2014 | UPDATED: 10:31 EST, 14 February 2014 A baby Prince Charles was 'fascinated' by his newborn sister Princess Anne, according to a rare letter written by the Queen just days after the birth. Less than two years old at the time, Charles treated Anne with 'great care', the Queen wrote to her friend Mrs Tanner. She also wrote that 'it will be fun when they are able to play together'. Family life: The Queen at her coronation (far left) Prince Charles (centre left) and Princess Anne (centre right) with their father The Duke of Edinburgh (far right)
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Letter written by the Queen after her daughter's birth to go up for auction
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The letter gives details of the Charles' reaction to his new sibling
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Auctioneers say emotional letter, estimate of £600, is an extremely rare find
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Most people who receive a letter from the Queen keep them, they say
'@placeholder has been a prolific letter writer over the years but most recipients have kept their letter.