I interview people, it's not my main job and I'm not in HR but I do it as a representative of the business iyswim. It is not an exact science.
It may be different for people who do it as a job, but for me the very very first interview I'm trying to gel with the other panel members, while also working out what the benchmark is going to be for this particular grade. I don't think it disadvantages the first candidate, but they become the initial point of comparison for the other candidates.
Last of the day can be more memorable, I agree, but also the interviewers may be tired or drained from the process and therefore potentially less receptive (not ideally, but it is what it is)
There are pros and cons to all slots. Before lunch, are tummies rumbling? After lunch, are they full and sleepy? I would honestly focus on what will work best for you, knowing yourself as you do.
For me, first thing would be best to get it over and done with. For friends, they prefer to have time to get up and ready at their leisure, get a coffee, go over cv etc, so later slots suit them better.
My best advice would be to be punctual but not excessively early, be polite and charming to every single person you interact with (I often glean a lot from the ushers about how candidates have acted towards them, it all helps build the picture of how they would be to work with), wear something smart but comfortable and give the interviewers the best version of yourself and your own performance. Deep breath, you will smash it!