Gunther Holtorf's 23-year road trip

Back in 1989, as the Berlin Wall fell, Gunther Holtorf and his wife Christine set out on what was meant to be an 18-month tour of Africa in their Mercedes Benz G Wagen. Now, with more than 800,000km (500,000 miles) on the clock, Gunther is still going.

The German former airline executive has travelled the equivalent of 20 times around the planet in the vehicle - which he calls Otto. He says he has never had a serious breakdown. Recently in Vietnam, Canadian-born photographer David Lemke joined Gunther on one section of his epic journey.