Investing in new European interconnection capacity is one strategy to integrate renewables and nuclear power stations in the electricity systems of GB and Ireland, by maximising their value through exports and meeting demand peaks through imports. This project aims to assess the value of UK interconnectors to the EU-27 and Norway, examining both the GB and the Irish Single Electricity markets, by investigating five hypotheses: 1. Expanding GB-linked interconnectors would reduce the cost of electricity for both the UK and the EU-27. 2. The operational value of interconnectors will be affected by post-Brexit market relationships (e.g. the GB relationship with the European Energy Union and the Irish Single Electricity market). 3. Balancing markets could be an important future source of revenue for interconnectors. 4. Previous interconnection modelling studies have misinterpreted spurious correlations caused by continent-wide increases in renewables and other system evolutions. 5. The optimal level of investment in GB and I-SEM interconnectors, and between Northern Ireland and the Republic of Ireland, in terms of both security and cost, will be affected by the outcome of Brexit negotiations. The ETM-UCL European energy system model and the ANTARES European electricity dispatch model are being used to assess the potential benefits of existing and new interconnection between the UK and the EU-27 and Norway, for a range of post-Brexit policy environments. The impact of interconnectors and renewables on electricity system stability is being assessed. The GCDCN model, adapted from neuroscience, is being developed to identify causal relationships between interconnection investments and price variations across UK and EU-27 markets. This provides a foundation for improving regulatory models and investment business case analyses.