Doubtless Sir Michael Quinlan sometimes talked about the tactical use of nuclear weapons on tank concentrations (Clifford Longley, Letters, 23 May). But he also had to deal with strategic nuclear issues. In a memo from 1978 he argued that, to be credible, the UK independent deterrent should have the capacity to kill up to 10 million Soviets. (See The Correspondence of Sir Michael Quinlan, ed. Tanya Ogilvie-White, 2011, published by IISS, p. 386, n. 75.) I think this fully justifies what I wrote