Complex sentence: The Social Democratic Party (SDP) was formed by prominent figures on the right of the Labour Party in early 1981, known as the "Gang of Four"-Shirley Williams, Roy Jenkins, David Owen and Bill Rodgers.
Split into simpler sentences: The Social Democratic Party (SDP) was formed by a split of some prominent figures on the right of the Labour Party in early 1981. Its main figures were the "Gang of Four"-Shirley Williams, Roy Jenkins, David Owen and Bill Rodgers.