People first started to write down stories about Arthur in the 10th century. The earliest stories about Arthur are in a Welsh book called the 'Mabinogion'. This book was for teaching people how to become bards. In 1136, a Welsh priest named Geoffrey of Monmouth wrote a book in Latin called "The History of the Kings of Britain". It was about lots of British Kings, but mostly about King Arthur. He claimed the stories he wrote were true. Throughout the middle ages, French writers like Chrétien de Troyes wrote lots more books about King Arthur (in French). They wrote as if Arthur lived in the Middle Ages like them. They added new bits to the story, like the Round Table, Sir Lancelot and the Holy Grail. They also added the idea of 'Chivalry' (being brave, fighting for right against wrong, having good manners & being nice to ladies). In 1470, an English knight named Sir Thomas Malory was thrown in prison because he owed people money. It was very boring in prison, so he wrote a long book called "The Death of Arthur". He wrote it in English. It was one of the first books in Britain ever to be printed instead of handwritten. There were lots of copies available. So King Arthur stories became very popular with everyone. The Victorian poet, Alfred, Lord Tennyson, wrote a famous group of poems about King Arthur and his knights called "The Idylls of the King". Lots of modern writers still tell stories about King Arthur. There are now films too, like "The Sword in the Stone", "Monty Python & the Holy Grail", "Excalibur", "First Knight" and "King Arthur".