The London Clay Formation is particularly susceptible to shrink–swell behaviour that has resulted in a long history of foundation damage owing to ground movement across the outcrop. Damage has cost up to £500 million in a single year. Underlying most of the Greater London area, the London Clay Formation is of major engineering importance as it is on and within this formation that the majority of the city's infrastructure, buildings and underground services are constructed. The Volume Change Potential (VCP) of a soil is the relative change in volume to be expected with changes in soil moisture content, and the subsequent shrinkage or swelling can cause major damage to structures above or below ground. Detailed statistical and spatial analyses of data across the London Clay outcrop have revealed a significant geographical trend in the VCP of this deposit, confirming an overall increase from west to east, but also showing subtle trends with depth. This paper describes how this analysis was carried out and shows how such assessments can yield valuable information about shrink–swell behaviour not only of the London Clay but also of similar shrink–swell-prone argillaceous formations elsewhere.