Two qualities define the Nile as the ultimate river. First, it is the world’s longest river. From the source in Rwanda to the end at the Mediterranean Sea, it travels 6650 kilometres (4130 miles). Second, the Nile is a truly cosmopolitan water. Its source lies in tropical Africa, its most important tributary – the Blue Nile – originates in the Ethiopian highlands. Its longest stage – through Sudan and Egypt – is characterised by Arab influences. Travelling through a sea of sand, this river gives life. It passes Africa’s largest city – Cairo – and ends only a few hundred kilometres away from Europe, in the Mediterranean Sea.

Explorer Levison Wood sets out on a nine-month walk along the length of the River Nile, visiting rainforests, deserts, cities and war zones, and encountering modern Africa, its people and its wildlife.

Pouring out of Lake Victoria, the Nile bursts into life, growing vast with sandy banks and mighty rapids. Under the scorching sun, elephant herds leave the savannah to drink and bathe in the river. This three-part series explores all the different faces of the world’s most ultimate river.

Joanna Lumley goes on the trip of a lifetime - exploring the longest river in the world, the River Nile, from sea to source.