This thesis examines the insights which may be gained from analysis of the potential for establishing a normative regime in English law for cohabitants, who now form a substantial constituency as an established alternative family unit, headed by apparently committed cohabiting couples, who are neither married nor in registered civil partnerships. The thesis critically analyses the 2006-7 work of the Law Commission in London, the apparent government reluctance to take this further despite Scottish implementation of a similar relationship generated compensation scheme on breakdown of such relationships, and the experience of other jurisdictions which have provided dedicated legislation for such families. The thesis also includes the results of some empirical fieldwork in qualitative studies with practitioners in a small number of key jurisdictions, including some comparative analysis of these experiences, and presents a theory which addresses the practical adverse impact of the lack of such a normative scheme in England and Wales. The thesis makes an original contribution to the debate on this area of English Family Law by providing a theoretical basis for legislation likely to be acceptable within the current modernisation of Family Justice in the recently established Family Court. It aims to meet both the drivers of that modernisation and most of the historic arguments against formally recognising (and discretely addressing the needs of) the substantial and continually growing cohabitant community. It makes further original contribution in analysing experience in the key jurisdictions which have introduced cohabitant legislation, both within our own geographical neighbourhood of the UK and EU and within the common law states of the Commonwealth, which were originally British settlements importing English law with them. Another original contribution is provided by an analysis of how such legislation could fit within the English legal system to provide a pragmatic solution to the escalating numbers of such families who now form a significant group expecting to find clarity in legal provision for their circumstances.