As Head of State, the Queen is a very busy women and she still has a packed diary despite celebrating her 93rd birthday this year.

And she has a lot of interesting and exciting hobbies to fill her time when she's not going through paperwork, meeting important people or getting updates on the country from the Prime Minister.

She enjoys horse riding and going for walks, but she also has a more unusual hobby which has earned her a LOT of cash over the years - about £100million to be exact.

The Monarch has been collecting stamps for decades and she now has an extremely impressive private collection.

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One of the most valuable in her stash is a Mauritian stamp, which alone was valued at a staggering £2million back in 2002.

The 1847 stamp from the Post Office of Mauritius is one of the most prized in the world, reports the Telegraph .

It originally belonged to her grandfather King George V, who bought it at auction in 1904. He paid £1,450 for the stamp at the time, which is equivalent to around £60,000 today.

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The stamp went on display to the public in 2002 as part of a travelling exhibition to celebrate the Queen's Golden Jubilee.

Over the years the Queen has added their own very impressive stamps to the growing collection, and it is now absolutely massive.

It is said to fill about 300 albums and about 200 boxes, which are all stored in a vault at St James's Palace.

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When the Queen took over the collection she decided to sell some of the "surplus to requirement" stamps at auction, and used the cash to buy new additions.

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According to the Telegraph , the pieces she sold were a huge hit with buyers back in 2001 and her 200 items made £750,000.

She spent £250,000 of the profit on a unique set of 10 Penny Blacks.