This thesis presents the findings of a research project to develop and implement a Lean and agile Construction System on a case study project. The aim of the research project, for the sponsor company, was to improve its projects site operations, making them safer for the worker and improving effectiveness and productivity. The findings have shown that the Construction System has proved to be a successful set of countermeasures that act as an antidote to the health, safety and productivity problems that exist in UK construction and that face the sponsor company. The System has been implemented on a large and complex mechanical and electrical case study project in the healthcare sector of UK construction. The outcome of this case study project shows that 37% less onsite labour was needed, meaning fewer workers were exposed to health and safety risks from site operations, leading to zero reportable accidents. Good ergonomics was achieved by focussing on workplace design, thus improving workers wellbeing, together with an improved quality of work for those required on site carrying out simpler assembly tasks. Productivity gains resulted by eliminating process waste, therefore reducing the risk of labour cost escalation that could otherwise have occurred. A 7% direct labour cost reduction was made meaning the labour budget allocation was maintained. Significantly, an overall productivity of 116% was achieved using the Construction System, which compares favourably to BSRIA's findings of an average overall productivity of only 37% when compared to observed best practice for the projects in that case study research. The results include the benefits found from the use of an innovative method to assemble, transport, and install frameless, preassembled mechanical and electrical services modules, where a 93% reduction in onsite labour was achieved together with an 8.62% cost benefit. No time slippage was experienced during onsite assembly to delay or disrupt other trades and the commissioning programme was not compressed that could otherwise have caused problems in handing over the facility to the customer. From a customer's perspective, the built facilities were handed over on-time, to their satisfaction and to budget. The research has achieved two levels of innovation, one at a process level and one at a product level. The process innovation is the development and successful implementation of the Construction System, which is a combination of methods acting together as an antidote to the research problem. The product innovation is the development of the innovative method for assembling, transporting and installing frameless mechanical and electrical corridor modules, whereby modularisation can be achieved with or without an offsite manufacturing capability. The System is built on Lean principles and has been shown to standardise the work, process and products to create flow, pull and value delivery. It is transferable across the sponsor company's business as well as the wider industry itself. The transformation that has occurred is the creation of a step-change in undertaking mechanical and electrical construction work, which has realised a significant improvement in performance for CHt that has "Transformed Traditional Mechanical and Electrical Construction into a Modern Process of Assembly".