I had the first interview with a nice woman who give me a feedback afterwards. Nothing difficult, introducing myself, say why Gartner..... The second interview lasted longer, 45min, and most of the question were competencies questions. Make sure you have examples of when you tried to convince someone or a group of person. They look for concise and clear example everytime. Be confident and calm, and everything might go well. the feedback they gave me at every interview were helpful.