The Secret Set band discussion has evolved/devolved into a "god, I hope it's..." conversation across all the forums.
Based on my own ill-conceived assumptions that the artist is going to be a.n.other of the euro-summer-rock-festival-acts, and of presumed stature to be second stage headliner/main stage support(ish) size,...
Then I'm going to punt at 5FDP.
Obvs they're a twat's band, but they do carry a mystifying level of popularity.
nb. At the risk of being even remotely close, I also made this point on the official forum a week or so ago.