In the fourth episode of the series, Commodus defeats his sister's coup but withdraws from governing, allowing others to amass power while he engages in an affair and banishes his wife.

Back one million years ago, South America was a continent of exotic oversized creatures found nowhere else on Earth - huge terror birds, giant ground sloths and spiky-tailed relatives of the armadillo as big as cars. The deadliest animal of them all was smilodon, the largest of the sabre-tooth cats, with canines like carving knives. The programme follows the fortunes of an individual male, Half Tooth. Ousted from his clan by a pair of rival males, his life suddenly becomes a struggle to survive in this alien world.

Scientists and engineers fight to save Notre Dame Cathedral after the 2019 fire. When the roof of Notre Dame Cathedral erupted in flames in April of 2019, firefighters battled for nine gruelling hours to save the historic landmark. Still, Paris came alarmingly close to losing more than 800 years of history. Now engineers are in a different race against time: to rebuild the roof and secure the medieval structure of Notre Dame. Underneath the charred scaffolding and vaulted ceilings of the cathedral, scientists study the components of Notre Dame’s iconic structure to puzzle out how best to repair it.

The Taiga forest, on the edge of the Arctic, is a silent world of stunted conifers. The trees may be small but filming from the air reveals its true scale. A third of all trees on Earth grow here and during the short summer they produce enough oxygen to change the atmosphere. In California General Sherman, a giant sequoia, is the largest living thing on the planet, ten times the size of a blue whale. The oldest organisms alive are bristlecone pines. At more than 4,000 years old they pre-date the pyramids. But the baobab forests of Madagascar are perhaps the strangest of all.

Waldemar Januszczak sets out to uncover the secret meanings hidden in four famous paintings by Van Gogh, Gauguin, Cezanne and Seurat. Everyone knows the pictures. They are among the most celebrated masterpieces of art. And yet, hidden inside them are codes and puzzles that no one has been able to decipher.
Van Gogh’s Self-Portrait with Bandaged Ear was painted soon after he cut off his ear with a razor. But how much do we really know about it? In a far-ranging investigation, Waldemar Januszczak delves into the clues hidden in the painting. The result is a tale of geishas, brothels, bullfights, love affairs, suffering and a fiery relationship with Gauguin. The work has a powerful secret message, if you know what to look for.

How do the five senses really work? In fact, there are many more than five, and they all work together to create our own version of reality. We dive into the stories of a pairs figure skating team, a perfumer, a cave explorer, and a musician to decipher how different ways of sensing the world all create their own vivid, and unique, picture.
This episode explores the world of human sensation and how it defines reality.