Right now in government, contingency planning is the order of the day. At the heart of it all, a flotilla of questions that begin with "what if?" The implications and consequences of the Iran war are already huge and hanging over everything is the biggest unanswered question of all: how long will this go on for? Ministers are guessing, just like the rest of us. For Chancellor Rachel Reeves there is an economic shock to react to, in real time. In the Commons later, she will focus on the domestic impact of the ongoing situation in the Middle East. I am told there will be three elements to her address to MPs, beginning with a short update on how the war is affecting the economy. There will also be a section on energy security, with a promise to crack on with delivering new nuclear power stations. The legislation to allow this to happen is expected later this year and will be set out in the King's Speech in May.…