In 2004 they rode around the world on their BMW R 1150 GS Adventure motorcycles, from London to New York, east to west -- accompanied by a camera crew.
This May the pair is preparing to ride again. Their 25,000 km journey on two new generation BMW R 1200 GS Adventure motorcycles starts at the most northerly point in mainland Britain, John O'Groats, Scotland and finishes at the most southerly point of Africa -- Cape Agulhas, South Africa.
The tour will take in 20 countries, including Libya, the Sudan, Ethiopia, Uganda, Rwanda, Tanzania, Botswana and the wilds of the Namibian Skeleton coast. The pair plan to visit several UNICEF sites which they say will provide inspiration and power to themselves and others.
"I can't imagine not ever thinking about some adventure," said Ewan McGregor.