Large scale project retrospectives from the trenches. An experience report from a big software company

You already know how to conduct the "Silver Bullet Retrospective" that solves all the problems you might be facing in your really big software development project? Then this experience report is not for you. If, on the other hand, you want to hear a real-world story about the challenges, pitfalls and success stories of a project retrospective for a big software development project in a large software development organization, then this talk might be right for you.
We'll tell you about some challenges that came about when, within our big software development department that is well on its way to employing and living Lean and Agile principles (using Scrum, Kanban and other Agile methodologies) with more than collaborating 20 Scrum Teams, an important development project was driven under high pressure both from the customer side and from top level management. We faced questions like "How can we continue living Lean and Agile principles while under pressure?", "How do we come to a sustainable velocity that fits the needs of both the employees and the customers?", and "How do we have to adapt our approach to planning, within our scaled Scrum setup?".
We addressed these topics in a big Open-Space-style Retrospective --- and in this talk we'll tell you how we put that into action, what preparations we found necessary, how we conducted the event, and --- most importantly --- what we did in order to sustainably implement the findings from the Retro.
As a key take-away we'll share our learnings on success factors of such a big project retrospective.