As construction materials are fixed to land or the structure of an existing building, they lose their identity as personal property and become part of the land itself. This basic proposition threatens to elevate the interest of the ultimate owner of the land, the freeholder, above the proprietors of temporally shorter estates in land, as the freeholder will ultimately stand to benefit from the works. English law has therefore developed a series of doctrinal rules in order to balance the different interests of freeholders, leaseholders, those with a security interest in the land, and the interests of participants in the construction project itself. Despite its doctrinal and practical significance, however, there is no unitary academic study analysing how construction operations affect different legal interests in the land. The thesis identifies the extent to which English law has a doctrinal framework that is consistent, with an identifiable doctrinal rationale, and formally certain and ascertainable, when it sets the balance between different interests in construction operations and legal interests in the land. It first considers the effect on interests in real property at the point of physical affixation of materials to the land. It then considers the effect of transfers of value on interests in land both in a contractual and extra-contractual framework. It finally looks at the impact on legal interests in occupation in the post-construction phase. The thesis concludes that English land law has arrived at a number of balances between the different interests in the land comprising the site which are capable of being formally ascertained and which have, for the most part, an identifiable rationale. There are, however, considerable doctrinal tensions between freehold and leasehold interests in the occupation phase of a building which require re-examination.