Judging by the lack of apparent progress in the Brexit negotiations over the summer, it would appear that Brussels and London are struggling to find many areas on which they agree. One exception is the broad consensus that the UK should continue to participate in European Union research programmes ¨C?for the next few years, at least.

That will suit the UK research community, which is almost unanimously in favour of joining Horizon Europe, the multibillion-euro successor programme to Horizon 2020. In May, the UK¡¯s science minister, Sam Gyimah, confirmed that the government shared that desire, but .?Last week¡¯s publication by the government of its position on Horizon 2020 and beyond confirms its desire to ¡°explore¡± association to Horizon Europe.

In the short term, it should be easy to pass Gyimah¡¯s fairness tests. Whatever deal is reached on UK participation for a few years after Brexit will be deemed ¡°fair¡± by the government.?During the 2019 spending review, the Treasury may start asking for evidence of the value of buying in to Horizon Europe, but it will probably not press too hard at this stage. Continued participation will be justified by politics rather than economics.

But the longer-term position is less clear. The UK¡¯s participation in previous EU research programmes has been underpinned by several arguments. The one most commonly cited by researchers is that it is a highly efficient way of creating pan-European partnerships, sustaining existing collaborations and pursuing high-quality research. Furthermore, EU money adds diversity to the funding ecosystem, sometimes supporting research topics ¨C archaeology, law and software engineering, for example ¨C that are lower priorities for domestic funders.

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In addition, the cost of participation has been included in the UK¡¯s overall subscription to the EU, so EU research funding did not appear to come at the expense of UK research budgets: it looked like ¡°free money¡±, with public accountability for it, in effect, delegated to the European Commission.

What¡¯s more, EU programmes have reflected the UK view that funding should follow excellence, rather than being spread evenly across member states. This played to the UK¡¯s scientific strength and allowed the country, in effect, to make a profit from participation.

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But while the popularity of EU initiatives among the UK research community will doubtless continue, the withdrawal of the UK¡¯s subscription to the EU post-Brexit will make the cost of participation all too transparent, and it may well be tensioned against other options for domestic UK science budgets.?

Moreover, with less UK influence on the design of Horizon Europe, policymakers in Brussels may divert more funds towards regional development, problem-solving missions and global challenges. Early signs of this are already visible in European Commission proposals. This means that the profit from participation in EU research programmes may disappear or even become a loss, either because the UK performs less well under the new rules or because of the terms of post-Brexit participation.

This suggests that the UK will face a stark new choice in the longer term: make payments directly to Brussels to participate in EU research programmes and accept a lower level of influence, or go it alone. The same amount of money could be spent through UK Research and Innovation, leaving that more clearly accountable body to choose between EU, global or local opportunities according to the best deals available.

If the UK no longer profits financially from participation in EU research, the rationale for participation will rest largely on the array of non-financial, intangible benefits ¨C such as enhanced international profile, access to international science facilities and participation in a larger pool of research talent ¨C that many UK researchers would claim derive from EU research collaboration.

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Appeal to such phenomena would be nothing new. The government invests in science and research to provide a public good rather than to make a profit, and for decades, public spending has been rightly justified by such indirect, often intangible, benefits. But the stark decision about whether to invest in UK or EU programmes will make it imperative to gather hard evidence of those benefits.

It will take time to develop robust techniques and datasets, but extensive evaluations and illustrations of the intangible benefits of research, innovation and scholarship have already been carried out in the UK and provide strong starting points.

For example, the Arts Council has many intangible benefits to people and society from investment in the arts. The Medical Research Council, the Wellcome Trust and the Academy of Medical Sciences a study on economic benefits of medical research. The puts a financial valuation on the natural environment.

These studies might seem distasteful to some people. But in the absence of financial valuations of intangible benefits, it is tempting for funders to assume those values to be zero. Without an explanation of the specific intangible benefits of EU collaboration, the case for future participation will inevitably be diluted.

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Graeme Reid is chair of science and research policy at UCL.