The European Solar Telescope (EST) will be a revolutionary Research Infrastructure that will play a major role in answering key questions in modern Solar Physics. This 4-meter class solar telescope, to be located in the Canary Islands, will provide solar physicists with the most advanced state-of-the-art observing tools to transform our understanding of the complex phenomena that drive the solar magnetic activity. The principal objective of the present Preparatory Phase is to provide both the EST international consortium and the funding agencies with a detailed plan regarding the implementation of EST. The specific objectives of the proposed preparatory phase are: (1) to explore possible legal frameworks and related governance schemes that can be used by agencies to jointly establish, construct and operate EST as a new research infrastructure, with the implementation of an intermediate temporary organisational structure, as a previous step for future phases of the project; (2) to explore funding schemes and funding sources for EST, including a proposal of financial models to make possible the combination of direct financial and in-kind contributions towards the construction and operation of EST; (3) to compare the two possible sites for EST in the Canary Islands Astronomical Observatories and prepare final site agreements; (4) to engage funding agencies and policy makers for a long-term commitment which guarantees the construction and operation phases of the Telescope; (5) to involve industry in the design of EST key elements to the required level of definition and validation for their final production; (6) to enhance and intensify outreach activities and strategic links with national agencies and the user communities of EST. To accomplish the aforementioned goals, this 4-year project, promoted by the European Association for Solar Telescopes (EAST) and the PRE-EST consortium, encompassing 23 research institutions from 16 countries, will set up the Project Office