Five months after submission (almost to the date) you get a communication through the participants portal. Subject: Initial information on the outcome of the evaluation of proposal submitted to the Call for proposal.... Heart stops for five millisecond and then starts beating furiously for the time it takes you to open the portal, sign in, retrieve and download the pdf and wait for the document to show up on your screen. And then fortunately it just takes a glance to see the words you are hoping for: 'I am pleased to'. You don't really need anything else. You passed the first stage and you get to go to the interview!
The letter gives you some basic info, including a bracket of time when your interview is going to take place, and then states that more info will follow in due time. About a month later you get the full pack: specific date and time bracket of your interview, instruction on what you'll be requested to do, details on the interview format, directions to the location (in the picture), etc. That's it, now you have to prepare for the interview. Let me just tell you this straight away: the fact that in the letter they give you a two-hours bracket for the interview doesn't mean you will have to wait there all that time (plus the 2 hours they tell you to be there in advance). Once you actually get to the building on the day they will assign you a specific time slot and you are only required to be there 20 minutes before. I'd like to say this right now because the idea of being in the room for potentially 4 hours without knowing exactly when I was going to be called was something that made me extra nervous.
As for the writing of the proposal, my only advice for the interview is practice, practice, practice. I am one of those people who never practice a talk in front of others, or even in front of the mirror, before a conference. But this is kind of too important not to. You have to nail it. Get it perfect being it in the content, the style, the images, the amount of writing on the slides, but especially the length. Getting it under 10 minutes was the most difficult thing for me and I only got there the week before the interview on what was probably attempt n. 20. And I am counting only the ones I gave publicly in front of people in sort of mock interviews.
I did loads of mock interviews with different audiences, but the most useful have been: the one I gave to a panel of other ERC grantees, organised by the Catalan Agency for Management of University and Research Grants (AGAUR), and the ones when I was filmed [yes, seriously! I hated it but was extremely helpful. Again, those involved know who they are and how grateful I am to them]. From what I could see, many institutions offer some sort of help with preparing for the interview. Take advantage of it. These are normally held quite in advance so it gives you plenty of time to refine your presentation based on the tips of people who went through it before you. Listen carefully to their advice but also critically and try to apply them and mould them to your personality. If you know that memorising things word by word doesn't work for you, don't try it even if someone says that's what they did! Talk to successful grantees, pick their brain not much on what the commission wants. Everyone will tell you the same: you have to be perfect, you have to be calm and confident, you have to let the panel understand that you believe in your project and you are able to carry it out, etc etc. Ask them their feeling, what they did before, how was the room they presented in, did they bring water in the room, how did they dress, was there a bathroom nearby the interview room, etc. Anything that, even if it seems stupid, will make you feel a little bit more at ease on the day.
Plan your trip to Brussels so that it is the least stressful. Personally, I got there the night before the interview and stayed in a hotel very close to the interview's location (the picture above was actually taken form my bedroom window). I like to scout places in advance so the evening before the interview I just strolled around the neighbourhood and got to have a look at the building. The day of the interview itself, I repeated a couple of times the presentation and then headed to the ERC building way in advance (I figured that waiting in the hotel or waiting over there was going to be the same). I got my presentation loaded and went up to the floor where the interview was going to take place and spent some time in the common room where I got to chat with other candidates. Again, this is really a personal thing but, for me, in order to really feel confortable in a place I have to have the hang of it, like knowing exactly where the vending machines are. So I spent quite some time there, in the waiting room, but also going to the cafeteria and the coffee cart. I had people tell me that their experience in the waiting room was quite awful: did not speak to anyone, everyone really tense, etc. I personally had a great time, talked to several people most of which were from other fields of research, got to hear their projects, chat about where they were from etc. Also saw a few people coming out from the interviews out of which only on was a little upset, all the others were quite positive. That somehow helped calming me down.
My interview was pretty much as I thought it would be. You get called and escorted to the door by an assistant to the panel. Then the President comes out and greets you. Once in a room he/she reminds you of what you are expected to do (in my case 10 minutes presentation and 15 minutes questions) and get introduced to the person who will lead the discussion. The presentation went as planned, finished in time and was reasonably clear. The first questions were the hardest, as I had problems in switching from presentation mood to question mood. But it got better and I think I had a great panel that understood that the hesitations at the beginning were more the result of this difficulty rather than real struggle with what to say. The last question put me a bit out of place as it was only very distantly related with what I do and what the project proposed so I had to honestly reply that I did not know what to say. It seems they appreciated the honesty since they decided to give me the grant!