Complex sentence: Sir Kenneth MacMillan (11 December 192929 October 1992) was a British ballet dancer and choreographer who was artistic director of the Royal Ballet in London between 1970 and 1977, and its principal choreographer from 1977 until his death.
Split into simpler sentences: Sir Kenneth MacMillan (11 December 192929 October 1992) was a British ballet dancer and choreographer. He was artistic director of the Royal Ballet in London between 1970 and 1977, and its principal choreographer from 1977 until his death.