The site investigation and the construction records for the Liverpool Loop and Link underground railway tunnels have been compared to see what lessons of good practice in site investigation emerge. The tunnels were constructed almost entirely within Triassic sandstones generally ranging in strength from weak to moderately strong, enabling roadheaders to be used effectively for most of the excavation. The report discusses the site investigation and the ground conditions as encounterered during construction in some detail. The site investigation was generaslly satisfactory, giving an accurate account of the geology of the site, accurately predicting the location of major faults and providing most of the ground information needed to drive the tunnels. However, during construction the rock was found to have more joints than had been suggested in the site investigation, no dought because of the difficulty of intercepting steeply inclined joints with a vertyical borehole. Trial shafts and headings are suggested to overcome this and other problems