This thesis introduces the substantive grounded theory of personal legitimising. It has emerged from a study of small consulting firms. Personal legitimising is about how individuals in organisations influence their work to take account of personal priorities and agendas. Colloquially, it can be described as consultants 'getting away with it' The theory introduces six behavioural categories. These are called 'opportunistic accommodating', 'sequential impressioning', 'voluntary championing', 'support mustering', 'pseudo endorsing' and 'retrospective justifying'. The first four are concerned with how individuals align personal and work agendas. The latter two report strategies that individuals use to defend their territory. Personal legitimising makes the distinction between those strategies which contain 'implicit' legitimacy and those which are 'explicit' in nature. With implicit strategies, people are able to chose the direction of their endeavours without recourse to management. This freedom is afforded by them operating within the bounds of 'organisational tolerance'. A comparison with literature in the substantive area of management consulting notes the presence of many of the ingredients of personal legitimising, but no theoretical explanation that links them together. The theory has implications for practitioners regarding the consequences on organisational strategy of individual actions, creating an appealing working environment for people (consultants) who are readily employable elsewhere, and the management of marketing. This is set in a context where knowledge based working is likely to account for an even greater proportion of enterprise in the future. The study also suggests further research in the area of impression management, and helps illuminate the practicalities of grounded theory study.