  The characterisation of exoplanets is critical to understanding planet
diversity and formation, their atmospheric composition and the potential for
life. This endeavour is greatly enhanced when light from the planet can be
spatially separated from that of the host star. One potential method is nulling
interferometry, where the contaminating starlight is removed via destructive
interference. The GLINT instrument is a photonic nulling interferometer with
novel capabilities that has now been demonstrated in on-sky testing. The
instrument fragments the telescope pupil into sub-apertures that are injected
into waveguides within a single-mode photonic chip. Here, all requisite beam
splitting, routing and recombination is performed using integrated photonic
components. We describe the design, construction and laboratory testing of our
GLINT pathfinder instrument. We then demonstrate the efficacy of this method on
sky at the Subaru Telescope, achieving a null-depth precision on sky of
$\sim10^{-4}$ and successfully determining the angular diameter of stars (via
their null-depth measurements) to milli-arcsecond accuracy. A statistical
method for analysing such data is described, along with an outline of the next
steps required to deploy this technique for cutting-edge science.
