To be perfectly honest with you it wasn't so bad :]
Presentation The meeting started with my presentation. I wasn't entirely sure what to present and there were no clear guidelines. Attempting to squeeze-in everything from my report seemed redundant, as (at least in theory) everyone on the committee would have read the report itself. Focusing on the broader picture didn't feel right either, I didn't think that giving the spotlight to the work of other people was the way to go while the panel was trying to assess how much progress I have made. In the end I decided to present my results, focusing on the analyses done between handing-in of the report and the viva (as those obviously weren't discussed in the report). I discussed any problems I had with analyses and asked for input. I thought it's a good idea to take advantage of four seasoned researchers when I have them all to myself!
Questioning After a while it was pointed out to me that this wasn't a research talk and that other aspects of my report and candidature should be discussed (maybe I took advantage of the researchers just a bit too much). Future plans were outlined and discussed, e.g. we talked about the next field season and agreed to have a meeting specifically about that in the near future (next week if possible).
Leave the room! Next, I was asked to leave the room while the committee members talk. It was a bit awkward to sit just outside as the room doesn't have solid walls, just glass, so you can see in and you know that the people inside are talking about you. Afterwards the supervisors left the room and I could talk to my thesis adviser.
We have discussed the fact that my current supervisor is re-locating; I was asked very directly (without my supervisor in the room) whether I had any worries or issues with the arrangements. I'm not worried and I think I can manage the change, so this was fine, but I'm not sure whether this is a way to have a conversation like that... Yes, my supervisor has left the room so that I could speak freely, but lets face it, if I had any issues it would have been pretty obvious as those would be discussed straight away when she enters the room again. Not much real confidentiality here.
Verdict
When everyone was back in the room I was told that I have officially passed my first year :]
Not on probation anymore! :]
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Feedback report - updated after receiving the report.
From the assessment report I received after the viva it sounds like I should have given more background during my talk and made sure that I'm putting my analyses in context ("presentation lacked a bit of context"). I need to explain better where there are holes in our knowledge and where the field is lacking data. I should point out how the questions I'm asking and the analyses I'm carrying out fill in those gaps. Fair enough!
The report ends witha note that "the meeting was very successful and the committee has no hesitation" about me progressing :]