George Robertson’s claims about the prime minister’s “corrosive complacency” over Britain’s safety made headlines. But it is a howl of pain, not a sober security analysis. The former Nato secretary general and author of the government’s strategic defence review (SDR) wants Downing Street to back his view of Britain’s role in the world – as Robin to America’s Batman – with billions of pounds of cash. But his argument takes for granted what should be under scrutiny: Britain’s global military role itself.

Donald Trump’s threats over Greenland, his disregard for international law and his U-turn over the Chagos deal expose the fragility of Britain’s defence assumptions. Before spending billions, those commitments must be re-examined. Lord Robertson’s claim of a £28bn black hole assumes that the current strategy is the correct one. But if that strategy –........

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