The Duke of Tintagel had opposed Uther Pendragon, King of England, for many years. When the Duke and his wife Igraine attended the royal court, King Uther desired his wife, but she refused him, and the Duke and his wife suddenly returned to their castle, leaving the King angry. He summoned them back, but they refused to return.
The Duke prepared for Uther to wage war against him by securing his wife Igraine in Tintagel Castle, and himself in Terrabyl Castle. Uther came with his army first to Terrabyl, where the fighting was fierce. Because of his anger at the Duke and his desire for his wife, Uther fell ill. Merlin was brought to heal the king, and promised him his desires, in return for the King following Merlin’s instructions. Those were that, when Igraine conceived on the first night that the King slept with her, Uther would give that baby to Merlin to raise as he wished, because of the great importance of their child. To ensure that Igraine became Uther’s willing partner, Merlin would transform the King to appear to her as her husband, the Duke of Tintagel.
The King rode off to Tintagel to set this in motion. As he did so, the Duke ventured out of Terrabyl Castle to take advantage of his absence. This proved a mistake, as the Duke was soon killed, before the King could even reach Tintagel and Igraine. That night, when she was still unaware of her husband’s death, she slept with the King, believing that he was the Duke, and Arthur was conceived. Early the following morning Merlin told the King to depart quickly, leaving Igraine to hear later of her husband’s death and wonder who she had slept with.
With Igraine now a widow, and the King in search of a wife, it was agreed that they should marry. After their wedding, the King told his wife the truth of how Arthur had been conceived, and admitted to being his father. This brought joy to his new bride.
Shortly afterwards, Merlin told the King that arrangements had to be made for the raising of Arthur, and proposed that Sir Ector should be asked to take on the task, and for his wife to become Arthur’s wet-nurse. Soon after his birth and before christening, the King was to give the infant to Merlin to take to Sir Ector. This was agreed, and two knights and two ladies delivered the newborn Arthur to Merlin, who was disguised as a beggar.

N. C. Wyeth’s illustration to the text “So the child was delivered unto Merlin, and so he bare it forth” from 1922 follows Malory’s account, with the knights and their ladies handing Arthur to Merlin.
When Sir Ector received the baby from Merlin, he was christened Arthur and nursed by the knight’s wife as they had arranged.

Emil Johann Lauffer’s undated Merlin Presenting the Future King Arthur, probably painted at the end of the eighteenth century, presumably shows Arthur being given to Sir Ector and his household.

Uther Pendragon’s legendary castle is now a ruin in Cumbria, in the north-west of England. Abraham Pether’s romantic View of Pendragon Castle by Moonlight was probably painted in the late 1700s.
Two years later King Uther fell sick, and his enemies seized the opportunity to wage war against him. Merlin told the King to join his army so they could be victorious, which they were. When Uther returned triumphantly to London, he lost the power of speech for three days, but Merlin told all his Barons to assemble before the King the next day. Merlin then asked the King whether his son Arthur should succeed him. In front of all assembled there, Uther confirmed that Arthur should be his successor. After he had given his son his blessing, the King died.
The kingdom then fell into disarray, with several of its Barons trying to claim the throne. To settle the matter, the Archbishop of Canterbury summoned them all to London for the feast of Christmas. After they had attended mass, they discovered a sword in an anvil outside in the churchyard. This anvil was mounted on a great stone, and written in gold around it was the inscription “Whoever pulls this sword from this stone and anvil is born the King of England”.
None of the Barons or others who tried to remove the sword from the anvil was able to do so. On New Year’s Day, more tried unsuccessfully to remove the sword. Among those attending the tournament there was Sir Ector, his natural son Sir Kay, and the young Arthur. When Sir Kay realised he had left his sword behind, he asked Arthur to ride back and fetch it.
Arthur was unable to get into their lodgings, so rode to the churchyard where the sword was still stuck fast in the anvil. He pulled it out with ease, rode back to Sir Kay and gave him the sword. As soon as Sir Kay saw the sword he recognised it, and rode to his father claiming that he should be made King of England.
Sir Ector took both the young men back to the church to swear on the Bible as to the true story of how Sir Kay came to have that sword. His son then admitted that it was Arthur who had given it to him. Sir Ector realised that it was Arthur who should be King, so got Arthur to put the sword back into the anvil and draw it out again, which he accomplished with ease.
Sir Ector then explained to Arthur the story of his origin and adoption. Later they went to the Archbishop of Canterbury, who had them replace the sword in the anvil, and called another meeting of the Barons at Candlemas to see if any of them could draw the sword from the anvil.

This miniature showing the young Arthur withdrawing the sword is one of a series made in about 1280, long before Malory wrote his account exactly two centuries later.
When the Barons were all gathered in the churchyard, no one else was able to draw the sword, until Arthur did so with ease. Some of the Barons demanded the matter should be deferred to another trial. This was repeated at Easter, when there were also many commoners present. They called for Arthur to be crowned king. Arthur was next made a knight, and was finally crowned King of England. He then settled some of the wrongs that had been done since King Uther’s death. Within a few years, he had won back all the lands of his kingdom, in the North, in Scotland, and in Wales too.
This initial story from Malory’s book didn’t become well known until T H White published his novel The Sword in the Stone in 1938, which became the first in his tetralogy The Once and Future King. It was also turned into very popular animated movie of the same title in 1963.
Reference
Dorsey Armstrong (translator and editor) & Sir Thomas Malory (2009) Morte Darthur, a new modern English translation, Parlor Press. ISBN 978 1 60235 103 5. (A superb translation based on the Winchester manuscript.)