Great question, and good point from Gwennael!
I would add that even if you are not leading the interview, you will still be judged on your ability to drive an independant piece of work. You might be cut in your reasonning and brought to a completely different aspect, and this is fine (it can be positive and negative, don't jump to conclusions)
What you need to focus on, is how to structure the smaller pieces of a big problem. When you hear questions as:
- What are the revenues drivers?
- What are the main costs?
- What could be the risks of doing this?
A red alarm should ring in your head: you need to structure.
For instance for the second question, NEVERstart a list of costs such as "Oh we can think about labour costs. Hum, also, hummm, raw materials, maybe. Silence. Also, distribution costs and hummm".
Instead, ask for 5-10 sec to think about the main costs and come with a structured answer: "I have identified three main costs: two variable costs and a fixed cost. The two variable costs are X and Y and the fixed cost is Z. Have I covered the most important costs or should I investigate further?"
The content is similar but you will definitely tick the box "structured" on a interviewer led case. You will notice that I structured the costs further, and this is generally appreciated. Often, when you have a possibility to create buckets, do it!
Another example is for risks, that can be structured into for instance: financial risks (for example currency), reputational risks (for example brand), "people" risk (for example union-related risks) etc.
I hope it helps!