A new 500kV DC photocathode electron gun is being developed at Jefferson Laboratory (JLab) with the aim of improving on the performance of the present FEL injector. The design benefits from the use of two inverted ceramic insulators to allow for a photocathode preparation chamber and load-lock system to be placed directly behind the gun. The electrostatic design emphasises the requirement to minimise the electric field gradients on the internal surfaces and incorporates shaped electrodes to provide some transverse focusing to the electron beam. Finally, provisions have been made to maintain ultra high vacuum conditions inside the gun chamber to prolong cathode lifetime during CW operation. This paper presents an overview of the electron gun and load-lock design.