Entitlement

I've just been listening to an interview with Ed Miliband. He was explaining, in a very brotherly way, that the choice of whether or not to be in the Shadow Cabinet was up to his brother, David (the one with the knife-handle sticking out of his back).

I don't understand much about Labour electoral practice. I know that electing the Labour leader is the only electoral process that rivals the elections to Church of England General Synod for Byzantine complexity and anomaly. But I'm still pretty sure that the way it works is not, that people called "Miliband" get to decide whether or not they are in the Shadow Cabinet. I'm pretty sure that the party has some kind of say in it. Or am I missing something?