  We provide a statistically robust and accurate framework to measure and track
the polarisation state of light employing Hong-Ou-Mandel interference. This is
achieved by combining the concepts of maximum likelihood estimation and Fisher
information applied to photon detection events. Such an approach ensures that
the Cram\'er-Rao bound is saturated and changes to the polarisation state are
established in an optimal manner. Using this method, we show that changes in
the linear polarisation state can be measured with 0.6 arcminute precision
(0.01 degrees).
