A novel rest gas ionisation profile monitor which aims to provide a continuous non-destructive bunch-by-bunch measurement of the transverse emittance is currently under development for the CERN Proton Synchrotron (CPS). Uniquely for this type of instrument the imaging detector that measures the position of the ionisation electrons consists of an array of pixelated silicon sensors which are read-out using Timepix3 readout chips. The pixel detector is directly sensitive to single ionisation electrons and therefore removes the need for electron amplification with Multi-Channel Plates which typically suffer from aging phenomena. The use of a pixel detector also offers the promise to significantly improve the time and spatial resolution of the position measurement compared to existing instruments. An ambitious program has been undertaken to develop a pixel detector that is compatible with operation directly inside the beam pipe vacuum together with the necessary radiation hard control and data acquisition electronics. A prototype version of the instrument was recently installed in the CPS and first results from the operation of this novel instrument will be presented.