  There is growing evidence that the majority of the energy density of the
universe is not baryonic or dark matter, rather it resides in an exotic
component with negative pressure. The nature of this `quintessence' influences
our view of the universe, modifying angular diameter and luminosity distances.
Here, we examine the influence of a quintessence component upon gravitational
lens time delays. As well as a static quintessence component, an evolving
equation of state is also considered. It is found that the equation of state of
the quintessence component and its evolution influence the value of the
Hubble's constant derived from gravitational lenses. However, the differences
between evolving and non-evolving cosmologies are relatively small. We
undertake a suite of Monte Carlo simulations to examine the potential
constraints that can be placed on the universal equation of state from the
monitoring of gravitational lens system, and demonstrate that at least an order
of magnitude more lenses than currently known will have to be discovered and
analysed to accurately probe any quintessence component.
