The C1 Advanced Writing paper is assessed against four criteria: Content, Organisation, Communicative Achievement, Language.
Each one asks something different about the same piece of writing.
They also have something in common. Much of the work happens before the writing begins. Deciding what to include, how to organise the response, which format the task requires, and what kind of language and voice it calls for are all part of the preparation. Practice is what makes those decisions quick enough to use under exam conditions. The writing stage is where those decisions are put into practice.

The new article looks at what each criterion actually asks, and how much of it is decided before a candidate writes a single sentence:

How much do your candidates already know about what gets decided before they start writing?