Martin Gilbert, Winston Churchill's official biographer, has died following a lengthy illness. He was 79.

John Chilcot, a senior civil servant, told a parliamentary committee on Wednesday that Gilbert died the previous night. Gilbert was a member of Chilcot's panel which is conducting an official investigation of the Iraq war.

Gilbert wrote more than 80 books, including many with themes related to the World War II. But he is best known for his work on Churchill, including "Churchill: A Life; "Churchill: The Power of Words," and "Continue to Pester, Nag, and Bite: Churchill's War Leadership."

Other titles include "Israel: A History," and the three-volume "History of the 20th Century."

Gilbert was knighted for services to British history and international relations.