White dwarfs in eclipsing close binary stars enable very precise timing. Within the past decade the number of such systems has grown rapidly and we now know of more than 55 white dwarfs in eclipsing detached systems and over 130 in cataclysmic variables. Departures in eclipse times from constant period ephemerides of order 10 to over 100 seconds have been seen from eclipse timing in many of these systems. A possible explanation for the variations in orbital period is the presence of low-mass bodies in wide orbits around the binary. This explanation is still not proven and variations intrinsic to the binaries themselves are hard to rule out for certain. One test of the planetary hypothesis is to demonstrate that the orbits are dynamically stable, and that they correctly predict eclipse times of the systems. Using observations taken with the highspeed camera ULTRACAM and the RISE camera on the Liverpool Telescope, we fit the observed deviations from the expected eclipse times with models that include one or two planets. We investigate the orbital stability of the resulting systems. In the case of the star NN Serpentis we find that the planetary model appears to provide a good predictor of the timing behaviour, and its orbits are dynamically stable over the 1 million years since its formation. Both detached white dwarf binaries and semi-detached cataclysmic variables show increasingly convincing evidence for circumbinary planets.