I didn't see his Host reveal coming from the first scene but when we saw him repeating the very same routine later on the penny dropped
People have pointed out the similarities with the opening scene of Lost season 2 (a Scottish man waking up in an underground bunker and going about his routine including riding an exercise bike whilst a 60s record plays) and I'm ashamed that I,
Lostie, didn't pick up on that
(although Lisa Joy says it was entirely coincidental anyway
)