I hope any Russian spies in the area take note of this because there's going to be more traffic than normal near/around/through Salisbury.
What a nightmare diversion. Similar road closures for the M56 have happened in the past. New bridge ready to be dropped in place but they need to demolish the old one first. Amazing they do it in such a short space of time really.
Part of the problem is that the official diversion has to suit all vehicles inc HGV. I know that area a bit and there are several shorter alternatives if you are in a smaller vehicle. These will however be very busy.