Lord Lawson, Chancellor in the Eighties, said he doubted Mrs Merkel would have needed to intervene ahead of Mr Cameron’s speech because open borders for workers was a prerequisite of EU membership. “What David Cameron is doing with benefits changes is welcome,” said Lord Lawson. “But the basic freedom of movement is an article of faith of the European Union. It is an essential part of their desire to create a single state. It would require a treaty change to alter it and that was never on.”