  We realise a quantum three-level system with photons distributed among three
different spatial and polarization modes. Ambiguous measurement of the state of
the qutrit are realised by blocking one out for the three modes at any one
time. Using these measurements we construct a test of a Leggett-Garg inequality
as well as tests of no-signalling-in-time for the measurements. We observe
violations of the Leggett-Garg inequality that can not be accounted for in
terms of signalling. Moreover, we tailor the qutrit dynamics such that both
ambiguous and unambiguous measurements are simultaneously non-signalling, which
is an essential step for the justification of the use of ambiguous measurements
in Leggett-Garg tests.
