Afterglow magnitude at the start of observation and redshift completeness as a function of follow-up delay for all the afterglows that have been followed up. The points have been coloured based on the redshift of the corresponding burst. Red symbols indicate GRBs without a measured redshift and arrows indicate bursts for which the afterglow was not detected in the acquisition image. In red is shown the redshift completeness as a function of follow-up delay.