Prompt gamma imaging (PGI) is nowadays a well-established technique for range control in particle therapy. However, the arrival time information of the particles needed for PGI is still affected either by accelerator related proton bunch drifts against the radio frequency in cyclotron facilities or by the irregular time microstructure of ion beams extracted in synchrotron facilities. Several solutions have been proposed to circumvent this issue, e.g. bunch monitors or hodoscopes. None of them have been capable so far to cope with the clinical high particle intensities within the full field of irradiation. We present a first clinical prototype of a hadron beam time tracker capable of detecting single particles within ion bunches with a time resolution below 1 ns. This prototype was able to provide time-of-flight information for the four beam species currently accelerated at clinical intensities at the Heidelberg Ion-Beam Therapy Center (HIT).