When do we start work? This seems like a simple question.
Sometimes it is simple to answer. If the work is a very simple task you can complete yourself, it is important and urgent - and you have nothing more important and urgent to do - then maybe start now.
If you have 10 same sized work items that each takes 10 colleagues 1 hour to complete - and the 10 people are half through completing item 3 out 10 and they need to complete all items as soon as possible - when should they start working on item 4?