This thesis presents new data on the work motivation of Metropolitan Police Service (MPS) constables. It offers data from two surveys: a snap-shot of the attitudes and behaviours of constables with seven years' service; and a survey of new recruits over their first fifteen months of service. It is perhaps the most comprehensive study undertaken of motivation to work hard and remain in a UK police force and includes a critical review of the motivation literature with specific reference to its relevance to the job of police constable. A provisional model is proposed to explain variance in the dependent variables - motivation to work hard (effort) and motivation to remain in the organisation (intention to stay/leave). New construct variables operationalise effort, reality shock, career frustration, organisational citizenship behaviour, socialisation and performance. Pre-existing scales are used for organisational commitment, management support, intention to leave, self efficacy, higher order need strength, organisational identification, intrinsic motivation and job satisfaction. The model met with a reasonable level of success: up to 46 per cent of the variance in intention to leave and up to 26 per cent of the variance in effort were explained. The effect of the model in explaining the outcomes of two organisational changes on the work motivation of experienced constables is also examined. Following the data analysis, a revised model is proposed. Motivation theories were shown to have validity and contribute to our understanding of work motivation. Variables explaining the work motivation of MPS constables were found to be similar to those in empirical research on other workers. However, probationary constables as a group were shown to have very unrealistic career expectations. Self-reported levels of effort decreased and levels of intention to leave increased over the socialisation period.