Simplify the following text for a Grade 10 native English-speaking person.
Original: Charles Peter Kennedy ( born 25 November 1959 ) is a British politician ; from 9 August 1999 until 7 January 2006 , he was the Leader of the Liberal Democrats , the third largest political party in the United Kingdom .
Simplified: From 9 August 1999 until 7 January 2006 , he was the leader of the Liberal Democrats , the third largest political party in the United Kingdom .