China has thrown down the gauntlet in an escalating trade war over the global steel glut, imposing punitive tariffs of 46pc on hi-tech steel produced in Britain and the rest of the European Union.

The astonishing move came as the Prime Minister, David Cameron, confronted the Chinese leader Xi Jinping at a meeting in Washington, pleading for action to slow the flood of Chinese steel exports reaching Europe.

The imminent demise of the Port Talbot steelworks and Tata’s wider steel operations in Britain has mushroomed within days into a full-blown national drama, calling into question the Government’s whole approach to China.