The values of the laser induced surface damage thresholds for samples of silicon, fused quartz and soda lime glass at both 0.248pm (UV) and 10.6pm (IR) are presented. Experiments are then described where laser damage is induced using crossed UV-IR beams, with varying time delays imposed between the arrivals of the two laser pulses at the sample surface. The results of these crossed beam experiments are then discussed. Order of magnitude reductions in the IR damage thresholds of silicon and glass are observed when the beams are crossed, no such reduction is observed for quartz. Further, only in the case of glass samples is a reduction in the UV damage threshold seen when the beams are crossed. The reduction in IR threshold on silicon has been seen with delays between the laser pulses of up to 100ns. The reduction in IR threshold for glass was seen for delays up to 1.2ms. These results lead to a discussion of the role of so-called seed electrons in the damage process and the mechanisms operative at the different wavelengths.