The evolution of the morphology of C/1999 S4 (LINEAR) is examined from a series of images taken from shortly before the disruption of the nucleus until 10 days afterwards. This is combined with light curve data to provide a unique documentation of the early evolution of the disruption event. Neither images from the 1-m Jacobus Kapteyn Telescope nor the 2.5-m Isaac Newton Telescope at the Roque de los Muchachos Observatory (La Palma, Canary Islands, Spain) show no evidence of bright sub-nuclei, although the presence of a well-defined stable lance-point structure in the head of the comet indicates that a dust and gas producing source remained active in this region. The centre of brightness of the coma moved in the anti-solar direction at a few tens of metres per second after disruption indicating that it was a mainly dust structure. The contrast in the fragmentation history of comets such as C/1999 S4, C/2001 A2 and 141P/Machholz 2 suggests that there is a wide variation in nucleus properties from highly unstable and loosely bound rubble piles to relatively consolidated conglomerates.