Rees was educated at Solihull School and Oxford University, and began his career as an editor on the BBC series Timewatch.

He wrote, directed and produced the 1997 series A Warning from History, the 2001 series Horror in the East, and the 2005 The Nazis and the 'Final Solution'. He has won many awards for his television films, including a BAFTA, a Grierson Award, an International Documentary Award, a British Press Guild Award and a BANFF festival award. He also wrote, directed and produced the documentary, World War II Behind Closed Doors.

He also wrote the companion books to his series A Warning from History, Japan and the Atrocities of World War II, When Hitler Fought Stalin and A New History. In 2006 he won History Book of the Year at the British Book Awards for his book on Auschwitz making him the first person to win both a BAFTA for a television series he has written, produced and directed, as well as a British Book Award for a book he has written.

His latest book, titled People Tested to the Extreme in WWII, was released in September 2007 by Ebury Press.

In 2005 he was awarded an Honorary Doctorate by Sheffield University for services to history and television.

In May 2010 he launched WW2History.com, a subscription multimedia educational resource on World War II