  Gamma-ray burst GRB 140430A was detected by the Swift satellite and observed
promptly with the imaging polarimeter RINGO3 mounted on the Liverpool
Telescope, with observations beginning while the prompt $\gamma$-ray emission
was still ongoing. In this paper, we present densely sampled (10-second
temporal resolution) early optical light curves in 3 optical bands and limits
to the degree of optical polarization. We compare optical, X-ray and gamma-ray
properties and present an analysis of the optical emission during a period of
high-energy flaring. The complex optical light curve cannot be explained merely
with a combination of forward and reverse shock emission from a standard
external shock, implying additional contribution of emission from internal
shock dissipation. We estimate an upper limit for time averaged optical
polarization during the prompt phase to be as low as P < 12% (1$\sigma$). This
suggests that the optical flares and early afterglow emission in this GRB are
not highly polarized. Alternatively, time averaging could mask the presence of
otherwise polarized components of distinct origin at different polarization
position angles.
