When in 1969 the specific task of scheduling shipping movements in and out of a tide-restricted port had been given as an exercise to a group of harbourmasters attending a symposium at UWIST, Cardiff, the varying methods employed and the apparently large workload involved indicated that a formal study of the problem would produce a more rational solution. The early part of the study, by K. D. Jones with the help of his assistant B. J. Moody, was to develop suitable computer programs to automate a scheduling process such that an ideal pre-movement plan could be arrived at, using as criteria the earliest movement times for given ship-draught and available water-depth.