  BL Lac objects detected at TeV energies preferentially belong to the subclass
called 'high-frequency-peaked' BL Lacs (HBLs). Parsec-scale radio jets in these
TeV-HBLs often show dominant, slow moving radio knots that are at most mildly
superluminal. We report the first systematic campaign to characterise the
Intra-Night Optical Variability (INOV) of TeV-HBLs using a representative
sample of 6 such sources, all showing a fairly high degree of optical
polarization. Our campaign consists of high-sensitivity monitoring of this
sample in 24 sessions of more than 3 hour duration each. For these TeV-HBLs, we
find a striking lack of INOV and based on this, we discuss the importance of
superluminal motion of the radio knots vis-a-vis the optical polarization, as
the key diagnostic for INOV detection.

High Energy Astrophysical Phenomena;Astrophysics of Galaxies