Seperating charged plates vs increased voltage

[Circlotron]

Suppose we have a pair of charged metal plates 100mm x 100mm separated by 1mm and in a vacuum. What's more, the potential difference between them is just below the voltage where a spark would jump between them. Now suppose we gradually draw the plates apart. As a consequence of the reduced capacitance because of the increased separation, the potential difference increases. Will the voltage increase faster than the separation difference so that at some distance it will flash over?

Also to be considered, the electrostatic attraction means we have to put some work into separating the plates so I expect this work would manifest itself in an even greater increase of potential difference than just by the reduction of capacitance alone. So, will it flash over at some increased separation distance ?