Why Was Walter Raleigh Beheaded?

Sir Walter Raleigh was beheaded by King James 1st of England, also known as Janes Vl of Scotland, supposedly for conspiracy.
Raleigh, like Drake, had been an English expolrer (and former pirate).  Also, like Drake, Walter Raleigh was a firm favourite with Queen Elizabeth 1st.
Between 1584 and 1587 he had tried, albeit unsuccessfully to establish a British colony in Virginia, North America.  Then in 1595, he made an exploration to the north coast of South America.  He brought back with him, both tobacco and potatoes, which ingratiated him to Queen Elizabeth who was proud that her explorers had achieved so much and had brought back new and exotic items.
However, after James 1st came to power in 1603, he set about ridding his court of all those who had been so favoured by the Queen.  One of the casualties of this policy was unfortunately Raleigh, although it is likely that he never really conspired against James.

He was falsely accused by king james I for conspiracy against him because walter raleigh blew up spanish ships under elizabeth I so the spanish king wanted james I to kill raleigh.