  At a high energy $ep$ collider, such as the Large Hadron-Electron Collider
(LHeC) which is being planned at CERN, one can access the $WW\gamma$ vertex
exclusively in charged current events with a radiated photon, with no
interference from the $WWZ$ vertex. We find that the azimuthal angle between
the jet and the missing momentum in each charged current event is a sensitive
probe of anomalous $WW\gamma$ couplings, and show that for quite reasonable
values of integrated luminosity, the LHeC can extend the discovery reach for
these couplings beyond all present experimental bounds.
