The chancellor's statement was supposed to be a gamechanger, but turned out to be an exercise in political survival.

When Jeremy Corbyn and Zarah Sultana announced a new political party this summer, it had all the ingredients to be a big success. But a summer of disarray has seen them overtaken by a rival on the left. What happened?

Three years ago travel writer Lydia Gard discovered freediving. An extreme and beautiful sport defined by one objective: to dive as deep as you can on one single breath. It soon became a calling. And then she stumbled on a darker side of the sport. Rumours were swirling that a group of top divers were doping to go deeper. So she decided to investigate. Deep Water is the latest Tortoise Investigates series from The Observer.