  This is an exposition a theorem of mathematical logic which only assumes the
notions of structure, elementary equivalence, and compactness (saturation).
Newelski proved that type-definable Lascar strong types have finite diameter.
Our exposition is based on a proof that appears in Pelaez' thesis - up to a
minor difference: the notion of weak c-free is replaced with the notion of
non-drifting that is introduced here.
