Complex sentence: He tries to hide himself in a political meeting, but is mistaken for the keynote speaker; he gives a rousing impromptu speech (without knowing a thing about the candidate he is introducing), but is recognised by Pamela, who gives him up once more.
Split into simpler sentences: He tries to hide himself in a political meeting where he is mistaken for the keynote speaker. He subsequently gives a rather rousing impromptu speech without knowing a single thing about the candidate he is introducing, but then he is recognised by Pamela, who gives him up once more.