Michael B, others - the lowering was just after sunset, say 7:45 pm, possibly a bit later as it was almost dark.,
The convergence line had just developed aided by outflow of the stuff further west earlier. The line than persisted as we know for several hours.
Surface winds were calm, although the lightning illuminated pic looks like an approaching guster, it was not, it was all training into the line and heading S/SW.
Nearest marked location on radar would be Dapto.