Robert Philpot seems to think that Jim Murphy’s support for a Trident nuclear replacement (“Scotland’s marathon man”, 6 December) puts him out of step with Ed Miliband’s “leftward drift”. There has been no sign of any such drift on this issue. If there is one, it is entirely imperceptible. What Murphy is out of step with is both current Catholic teaching and common sense. Threats to commit mass murder, morally indefensible anyway, are of little security