Redshift drift of gravitational lensing

We investigate the effect of the redshift drift in strong gravitational lensing. The redshift drift produces a time variation of (i) the apparent position of a lensed source and (ii) the time delay among incoming signals from different images. We dub these effects as angular drift and time delay drift and show that they are of order of 10-10 arc seconds per year and 10-3 seconds per year, respectively. With present techniques there is apparently no hope of detecting such small changes for time intervals smaller than 109 years.