Trust and calculation in international negotiations: How trust was lost after Brexit

How does a loss of trust affect international negotiations? We know that trust enables cooperation and comes with the risk of betrayal. Yet the effects of lost trust are not well understood, with most research in International Relations (IR) focusing on how trust is initially built in adversarial relations. In this article, we conceptualize trust as the eclipsing of possible futures in which others do not behave cooperatively. When trust is lost, actors include further possibilities of non-cooperative behavior in their calculations and adjust their negotiating demands accordingly. We use this framework to explain the European Commission's response to Boris Johnson's government breaking its trust during the Brexit negotiations by deviating from the Political Declaration, introducing the Internal Market Bill, and not conducting border checks in the Irish Sea. Drawing on elite interviews, we trace how the Commission altered its expectations and consequently sought negotiated outcomes with tighter contracting, reduced discretion and retaliatory mechanisms. Analysing the interplay of trust and calculation on a granular level, we show that breaches of trust do not preclude future cooperation per se, but shape its form and extent in important ways.