Understanding the behaviour of the Internet with its inherent complexity and scale is essential when designing new Internet systems and applications. Simulation, emulation, and test-bed experiments are important techniques for investigating large-scale complex Internet systems. It is now widely recognised that classical theoretical/simulation scalability studies for Internet research are unreliable without relevant and representative supporting experimental evidence. This is increasingly important with the emergence of 5G, cloud services and IoT, which lead to at least 2 orders increase in connection capacity requirements and 3 orders of additional devices that require Internet connectivity. Great progress has been made in the UK over the years on the development of communications laboratories infrastructure in ICT domains such as optical & wireless, signal processing, networks and distributed systems, where the UK is internationally leading. However, UK telecommunications research remains largely segregated in independent optical, wireless or computer network research labs, so researchers very rarely have the opportunity to experiment across the boundaries between these disciplines. Due to the limitations of performing research in discipline-specific facilities, the current UK ICT research output does not address realistic end-to-end Internet systems INITIATE will create a new, specialist distributed test-bed to facilitate the increasingly large and complex experimentation required for future Internet research. This will be achieved by interconnecting operational, state-of-the-art operational laboratories at the Universities of Bristol, Lancaster (UoLan), Edinburgh (UoEd) and Kings College London (KCL). These laboratories will contribute many key capabilities for Internet research including optical networks, wireless/RF communications, the Internet of Things (IoT), Software Defined Networking (SDN), Network Function Virtualisation (NFV) and cloud computing. Therefore INITIATE will offer the combined capability to the UK Internet research and innovation communities as a single distributed test-bed able to support the increasingly complex experimentation required for future Internet research. For example, INITIATE will enable for the first time experimentally driven research addressing the integration of multi-domain and multi-technology 5G and IoT access platforms with high-speed optical transport and investigate full system optimization strategies. Uniquely, INITIATE will also be able to integrate end-users as part of the experimental process and support user driven scenarios such as mobile edge computing, data visualization and autonomous mobility. The applicants have an outstanding worldwide reputation for creating, maintaining and operating research test-beds. They have repeatedly enabled remote access to their laboratories for experimenters and they have worked in multiple initiatives involving interconnection of research test-beds either locally, across the consortium partners or at a regional, national and international scale. Examples are: Bristol Is Open (UoB), TOUCAN (EPSRC involving UoB, UoEd, UoLan), NDFIS (UoB, UCL, SOTON, Cambridge), wireless mesh networks for rural communities (UoLan) and the Ofcom whitespace trial environment (KCL), among others. Internationally, the partners have been involved in numerous Future Internet infrastructure projects such as OFELIA & Fed4FIRE (EU FIRE), FIBRE & FUTEBOL (EU-Brazil), STRAUSS (EU-Japan) and GEANT, where they have delivered test-bed infrastructure, developed experimental control and federation tools and supported user experiments. INITIATE will create an environment for delivering excellence in Internet research, educational and industrial innovation and cross-discipline interaction through experimentally driven national collaboration. The project will also support academia as well as industry and SMEs and will deliver a sustainable engagement model.