AbstractWhen the results of the 3rd Geodetic Levelling of England and Wales, which was observed between 1952 and 1956, were analysed and compared with the results of the 2nd Geodetic Levelling (1912–1921), certain significant points came to notice. These points have already been discussed elsewhere [1, 2, 3, 4], but as their implications may affect a number of organisations that have not had access to these papers, it is believed that some account in a widely read journal, such asThe Survey Review, is warranted. Briefly, it was found virtually impossible to reconcile the apparent movements of the land as revealed by a comparison of the levellings either with known tectonic trends or with records of the three tide gauges to which both the levellings had been referred. It was thought that a possible cause of these discrepancies might be a systematic error introduced into levelling extending in a North-South direction by a tendency for the levelling staves to give a slightly lower reading when illuminated by direct sunlight than they did in the shade.