Storm clouds gather on Capitol Hill for Tik Tok as US Congress holds hearing on the Chinese-owned social media giant .

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Also on the programme: The death of a head teacher prompts calls for Ofsted inspections to be paused. We speak to a former education secretary. A major UN report warns that if the catastrophic effects of global warming are to be slowed, there will need to be radical reductions in the use of fossil fuels. But the UN's top climate official tells us there is still time to act. And a heated debate on whether the Elgin Marbles should be loaned to Greece by the British Museum.