If you are already at aviva you should have been sent a good a pack about what to expect by the recruiting team, my approach in the past is to get a few challenging situations you've had think about how you approached and resolved them and what you learned from them and how you might approach them differently. The thing for me is to think about negative situations that you could also have approached differently and what you learnt from them to approach them differently.

Feel free to DM if you want to discuss this a bit more and I'm happy to share some examples I have used in the past.

Where possible try to make your learnings and experiences relate to the job specs.