 Bradshaw and Bayes Bradshaw and Bayes: Towards a Timetable for the Neolithic is necessary to introduce a series of papers on a group of long barrows in southern England with a justiica- tion of why we have devoted so much time and energy to unravelling the details of their chronology. And we will not bluf you with ‘date-substitutes’; by chronol- ogy we do mean Bradshaw — explicit, quantitative, probabilistic estimates of real dates when things hap- pened by the agency of particular people in speciic places in Neolithic southern England. Chronology is fundamental to archaeological study. First, it allows variations in the archaeological record which depend upon time to be distinguished from those determined by other factors. In this case chronologies can be relative or absolute, since what Alex Bayliss, Christopher Bronk Ramsey, Johannes van der Plicht & Alasdair Whitle The importance of chronology is reasserted as a means to achieving history and a sense of temporality. A range of current methods for estimating the dates and durations of archaeo- logical processes and events are considered, including visual inspection of graphs and tables of calibrated dates and the summing of the probability distributions of calibrated dates. These approaches are found wanting. The Bayesian statistical framework is introduced, and a worked example presents simulated radiocarbon dates as a demonstration of the explicit, quantiied, probabilistic estimates now possible on a routine basis. Using this example, the reliability of the chronologies presented for the ive long barrows considered in this series of papers is explored. It is essential that the ‘informative’ prior beliefs in a chronological model are correct. If they are not, the dating suggested by the model will be incorrect. In contrast, the ‘uninformative’ prior beliefs have to be grossly incorrect before the outputs of the model are importantly wrong. It is also vital that the radiocarbon ages included in a model are accurate, and that their errors are correctly estimated. If they are not, the dating suggested by a model may also be importantly wrong. Strenuous efort and rigorous atention to archaeological and scientiic detail are inescapable if reliable chronologies are to be built. The dates presented in the following papers are based on models. ‘All models are wrong, some models are useful’ (Box 1979, 202). We hope readers will ind them useful, and will employ ‘worry selectivity’ to determine whether and how each model may be importantly wrong. The questions demand the timetable, and our prehistories deserve both. It may seem reactionary and perverse to reairm, as I do, at the beginning of a book on archaeology in the ield that mere dates are still of primary and ultimate and unrelenting importance. And by dates I mean not simply those nebulous phases and sequences, those date-substitutes, with which archaeologists oten try to bluf us. I mean time in hard igures. I mean Bradshaw (Wheeler 956, 38). A ‘Bradshaw’ was a colloquial designation of Brad- shaw’s Railway Guide, a timetable of all railway trains running in Great Britain, printed annually from 839–96.  It is salutary, 50 years and several radio- carbon revolutions ater Wheeler wrote, that we feel it Cambridge Archaeological Journal 7: (suppl.), –28 © 2007 McDonald Institute for Archaeological Research doi:0.07/S095977430700045 Printed in the United Kingdom.