Sir, – There is a ghost that needs to be laid. There is a popular belief that the Treasury used to give extra money to the MoD to cover the cost of Trident which was, therefore, somehow outside and an addition to, the defence budget, and that they, the Treasury, have somehow subsequently renegued on this agreement . This is simply untrue. When in 1979, the then Defence Secretary, Francis Pym, made a statement to the House of Commons on the replacement of the UK’s Polaris strategic nuclear deterrent system with Trident, he confirmed that the capital cost of procuring Trident would be taken out…